Preparation of monodispersed PNIPAm/silica composites and characterization of their thermal behaviors
Yong-Geun Lee,Chang-Yong Park,Kyung-Ho Song,Sung-Soo Kim,Seong-Geun Oh*
Department of Chemical Engineering,Hanyang University,17Haengdang-dong,Seongdong-gu,Seoul133-791,Republic of Korea
1.Introduction
The creation of new hybrid materials has focused on the
preparation of signi?cant organic–inorganic materials[1,2],
because they exhibit good mechanical properties and biocompati-
bility simultaneously.The functional hybrid materials have found
diverse applications in diagnostic,coating,and catalyst because of
their novel and excellent properties such as mechanical,chemical,
electrical,rheological,magnetic and catalytic,by varying their
composition,dimension,and structure of the materials[3–8].
Notably,silica[9–11]is a useful material as a substrate of
hybrid materials which can be controlled easily depending on the
various synthetic factors such as temperature,pH,and concentra-
tion of reactants.Also,silica materials offer many advantages to the
hybrid materials.When the hybrid materials were made using a
silica sources,they show a better mechanical strength with
improved chemical and thermal stability together.Moreover,they
do not swell in most solvents,which prevent the degradation of
entrapped bimolecular components.
To modify the hybrid materials which can be applied for DDS
(Drug Delivery System),many strategies have been tried to release
the encapsulated drug sources effectively.However,the driving
forces for release of the encapsulated species are limited to osmotic
pressure,rupture of outer shell and diffusion.These limitations
highlight the need for fabrication of hybrid particles with new
properties,which can respond to the changes of temperature,pH,
electric?eld or light intensity.
In recent years,poly(N-isopropylacrylamide)(PNIPAm)is one
of the most commonly studied stimuli-responsive polymers.
Generally,poly(N-isopropylacrylamide)-based microspheres and
micelles have been synthesized via emulsion polymerization[12],
inverse suspension polymerization[13],and self-assembly of
poly(ethylene oxide)-b-(N,N-dimethylacrylamide-s-N-acryloxy-
succinimide)-b NIPAm block polymers[14].In particular,this
polymer has both lower critical solution temperature(LCST)and
upper critical solution temperature(UCST)interestingly.The linear
polymer of PNIPAm provides a nonionic water soluble property
with a lower critical solution temperature(LCST)of$328C[15].It
swells below318C and shrinks above328C in aqueous solution,
which means that PNIPAm releases most of its water content above
328C.Due to their well-known temperature-responsive property
with a LCST of around328C,PNIPAm can be easily applied in the
area of bio-medical science.
The silica/polymer hybrid/composite particles with various
interesting morphologies,such as silica core/organic shell[16],
organic core/silica shell[17],raspberry-like[18],snowman-like
[19],daisy-shaped and multipod-like[20],and raisin bun-like[21]
have been afforded by different techniques.
In this study,we report a facile and successful synthesis of
PNIPAm/silica core–shell hybrid spheres for the?rst time.First
type of hybrid materials is a PNIPAm polymer grafted silica hybrid
particles(silica is a core material and PNIPAm polymer is a shell
material).In our previous work,VTMS silica spheres as a substrate
were prepared using a remodeled sol–gel reaction[22].Because
Journal of Industrial and Engineering Chemistry18(2012)744–751
A R T I C L E I N F O
Article history:
Received15June2011
Accepted23July2011
Available online12November2011
Keywords:
Hybrid materials
Silica
PNIPAm
Vinyl trimethoxysilane
Phase transition temperature
A B S T R A C T
Two types of thermosensitive poly(N-isopropylacrylamide)(PNIPAm)-silica organic/inorganic hybrid
particles were successfully prepared in aqueous solution through a facile synthetic process.Silane
coupler of vinyl organic groups connects the PNIPAm to silica.First,hybrid spheres were prepared by
grafting PNIPAm polymers to VTMS(vinyl trimethoxysilane)silica spheres.The thickness of polymer
shell on the silica surfaces could be easily controlled by varying the concentrations of NIPAm monomer.
Second,another type of hybrid particle was fabricated by encapsulating PNIPAm polymer with silica
materials.The PNIPAm polymers were completely encapsulated by silica shell.The morphologies and
shell thickness were characterized through SEM and TEM.The variations of phase transition temperature
of PNIPAm were measured using DSC.
?2011The Korean Society of Industrial and Engineering Chemistry.Published by Elsevier B.V.All rights
reserved.
*Corresponding author.Tel.:+82222200485;fax:+82222944568.
E-mail address:seongoh@hanyang.ac.kr(S.-G.Oh).
Contents lists available at SciVerse ScienceDirect
Journal of Industrial and Engineering Chemistry
j ou r n al h o m e p a g e:w w w.e l se v i e r.co m/l oc a t e/j i e c
1226-086X/$–see front matter?2011The Korean Society of Industrial and Engineering Chemistry.Published by Elsevier B.V.All rights reserved.
doi:10.1016/j.jiec.2011.11.117
the VTMS silica particles have a large amount of vinyl groups on the surfaces,PNIPAm polymer can be effectively attached to the silica substrate through the copolymerization.Also,shell thickness could be controlled by changing the concentration of polymer.Second type is a silica coated PNIPAm hybrid nano particles (PNIPAm polymer is a core material and silica is a shell material).Using an as-prepared NIPAm–VTMS oligomer,PNIPAm polymer can be easily entrapped into the silica spheres.The characteristics of hybrid silica particles were investigated by SEM,TEM,TGA,FT-IR,DSC and NMR measurements.
2.Experimental
2.1.Materials
Vinyl trimethoxysilane as a silica source,N,N-methylenebi-sacrylamide (MBA)as a crosslinker of polymerization,and potassium peroxydisulfate (KPS)as an initiator of polymerization were purchased from Sigma–Aldrich Chemical Company.Ammo-nium hydroxide (NH 4OH,25%)as a catalyst for the formation of silica was given from Wako Pure Chemical Industries.N-isopropylacrylamide (NIPAM)as a monomer of PNIPAm was obtained from Acros Organics.Acetone,ethanol,and methanol were purchased from Duksan Pure Chemical Company.All chemicals were used as received without further puri?cation.Water was obtained from Milli-Q water puri?cation system (Millipore).
2.2.Preparation of vinyl-functionalized silica (VTMS silica)particles
The 10g of VTMS was added into 100g of water with stirring until the oil (VTMS)droplets have completely disappeared and a transparent solution was obtained.NH 4OH (0.1mL)was added to the mixture solution,and then the reaction was progressed during 12h at room temperature.After completion of the reaction,the resulting precipitates (VTMS silica)were centrifuged and washed several times using alcohol.
2.3.Preparation of PNIPAm coated hybrid silica particles
Polymer/inorganic hybrid silica particles were synthesized by radical copolymerization of VTMS silica with NIPAm monomers.The 0.015g of KPS was added into the 10g of water,and then the 1.35g of ethanol solution including 0.15g of VTMS silica particles was added into the KPS solution.Next,this solution was added into the 10g of water solution containing 0.05g of MBA and NIPAm monomer with stirring.With increasing the concentration of NIPAm monomer to 0.15g,0.3g,0.45g,and 0.6g,formation of particles was examined.The solution heated at 708C for 12h and the PNIPAm coated hybrid silica particle can be obtained.The particles were centrifuged at 3000rpm for 15min and washed several times with methanol to remove the remainders.The powders were dried in a vacuum oven at room temperature for 24h.
2.4.Preparation of hybrid silica particles encapsulating PNIPAm polymer
The 0.4g of NIPAm monomer,0.03g of MBA,and 0.5mL of VTMS were added into the 20g of water with vigorous stirring.After 30min of mixing,the 10g of water solution including 0.01g of KPS was added into the NIPAm solution.Next,the solution was heated to 808C to synthesize the PNIPAm core particle.After 12h of reaction,the 0.25g of VTMS and 0.3mL of NH 4OH were added to prepare the shell structure comprised of silica materials.The reaction was carried out for 12h at room temperature.The resulting precipitate was centrifuged and washed several times with ethanol.
2.5.Characterizations
Field emission scanning electron microscopy (FE-SEM,JEOL Co.Model JSA 840A and JSM-6700)was used to observe
the
Fig.1.SEM images of silica spheres prepared using VTMS organosilane at different
magni?cations.
Fig.2.Schematic representation of the formation of PNIPAm polymer/silica hybrid particles.
Y.-G.Lee et al./Journal of Industrial and Engineering Chemistry 18(2012)744–751
745
morphology of the particles.Before the FE-SEM investigation,samples were coated with platinum by sputtering for 3min.The transmission electron microscopy (TEM)pictures were taken through JEOL JEM-2000EXII microscope operating at 200kV.The samples of TEM are obtained by dispersing a small dropping of the suspension with lower concentration onto a copper grid pre-coated with amorphous carbon.And then,the TEM grid was dried in drying oven at 408C for 1day.For TGA measurements,samples were tested with a TGA7(PerkinElmer)Thermogravimetric Analyzer.All tests were performed under atmospheric pressure.The heating rate was 28C min à1from 25to 7008C.The LSCT of poly-(NIPAM)grafted hollow silica particles were characterized by Differential Scanning Calorimetry (DSC2010,TA instrument)between 10and 508C at the rate of 28C min à1under nitrogen atmosphere.
3.Results and discussion
3.1.Preparation of PNIPAm polymer grafted silica hybrid particles
SEM images (Fig.1)show the VTMS silica particles prepared by the simple one-step reaction in aqueous solution.VTMS silica is composed of many vinyl groups and showed uniform spherical shape with average diameter of about 1m https://www.doczj.com/doc/b115544366.html,ing a VTMS silica particles as a substrate,it was possible to prepare the highly monodispersed PNIPAm/silica particles consisting of core–shell hybrid structure (Fig.2).
The thickness of PNIPAm polymer on the surface of silica particles at different weight ratios (NV,NIPAm monomer/VTMS silica)are shown in Fig.3.In the case of VTMS silica particles,they have a large amount of vinyl organic groups on their surfaces.So,after polymerization of NIPAm monomer,PNIPAm polymer can
be
Fig.3.Typical TEM images of hybrid PNIPAm/silica particles with varied PNIPAm shell thickness at different weight ratios (NV,NIPAm monomer/VTMS silica):(A)NV =1,(B)NV =2,(C)NV =3,and (D)NV =
4.
Fig. 4.Relationship between the thickness of PNIPAm polymer and the concentration of NIPAm monomer.
Y.-G.Lee et al./Journal of Industrial and Engineering Chemistry 18(2012)744–751
746
easily attached to the silica surface.The inset TEM picture con?rms that the particles are spherical shape.When the NV is 1,the thickness of PNIPAm is small and approximately 6nm.In contrast to the TEM images shown in Fig.3A,Fig.3B–D shows the core–shell structure clearly.When the amount of NV increases to 2,a thicker shell of PNIPAm is formed about 10.5nm on the silica surfaces.Interestingly,with the further increase of NV to 3and 4,the thickness of polymer increases to approximately 13.7nm and 17.9nm and the core–shell structure become more regular and distinguishable.As a result,it can be found that the
thickness of PNIPAm polymer increases with the increases of an amount of NIPAm monomer.Also,low NIPAm concentration cannot lead to the successful formation of PNIPAm/silica hybrid particles.Fig.4summarizes the relationship between the thickness of polymer shells and various concentrations of NIPAm monomer.
The amount of PNIPAm polymer grafted onto the silica surfaces was investigated by TGA curves as shown in Fig.5.An overall weight loss of $5%was attributed to the evaporation of physisorbed and chemisorbed water.The major
thermal
Fig.6.FT-IR spectra provide evidence of the PNIPAm/silica hybrid particles.(A)VTMS silica particles and (B)PNIPAm/silica hybrid
particles.
Fig.7.DSC thermograms of samples:(A)NV =1,(B)NV =2,(C)NV =3,and (D)NV =
4.
Fig.5.TGA curve of samples:(A)VTMS particles,(B)NV =1,(C)NV =2,(D)NV =3,and (E)NV =4.The initial weight loss is due to the evaporation of residual water,while the two-step weight loss is due to the degradation of PNIPAm.When the NV is 4,the highest weight loss was revealed.
Y.-G.Lee et al./Journal of Industrial and Engineering Chemistry 18(2012)744–751
747
degradation of material is appeared at 300–5008C,which supports that the most polymers were removed.There is a minor weight loss between 500and 7008C,which can be attributed to the release of gases formed during the decomposition process.
Especially,the weight loss rates of the hybrid particles were increased as the values of NV increased.When the NV values are 1and 2,weight loss of polymer was revealed around 18%and 25%,respectively.Moreover,when the NV is 3,overall polymer weight lose is showed as about 40%.The highest concentration of NIPAm monomer (NV is 4)led to noticeable weight loss to 60%due to the large amount of polymer degradation grafted onto the silica surface.SiO 2could not be decomposed in the experimental temperature range.It is clear from the TGA data that the amount of NIPAm monomer leads to the growth of the shell thickness on the particle surface.
To identify the presence of molecular structure of as-synthe-sized VTMS silica spheres,FT-IR measurement was conducted [23].Fig.6A shows the FT-IR spectra of VTMS-silica bare particle.The asymmetric stretching vibrations of the siloxane (Si–O–Si)appear between 1200and 1000cm à1,and the symmetric stretching vibrations of the siloxane (Si–O–Si)appear at 800cm à1in the spectra of all the samples.The band at 3700–3200cm à1,which is attributed to the stretching vibration of Si–OH in silanol group,is also the typical band of silica,and the broad peaks at $3350and 1620cm à1indicated that silica contains the large amounts of adsorbed water in atmospheric moisture.Obvious peak at 1600cm à1is due to the presence of C 55C group in VTMS.However,in contrast to the IR data of VTMS silica particles,PNIPAm
grafted
Fig.8.The scheme for the formation of hybrid silica particles encapsulating PNIPAm
polymer.
Fig.9.SEM (A)and TEM (B)images of hybrid spheres fabricated by NIPAm–VTMS
precursor.
Fig.10.TEM image of hollow silica shell after removal of PNIPAm core.
Y.-G.Lee et al./Journal of Industrial and Engineering Chemistry 18(2012)744–751
748
silica reveals the different peaks.In the spectrum of PNIPAm grafted hybrid silica particles(Fig.6B),a new absorption band of C55O at1700cmà1is observed.These results con?rm that PNIPAm are grafted onto the surface of VTMS silica particles.
DSC was used to study physical properties of the hybrid materials as shown in Fig.7.An endothermic point could be seen owing to the phase transition of PNIPAm,and the maximum endothermic peaks of the sample around348C are de?ned as the phase transition temperature(LCST)[24].When the NV values were1and2,the endothermic peaks were not clearly detected due to the small amount of PNIPAm in hybrid particles.In contrast to the LCST of pure PNIPAm(328C),the LCST of PNIPAm grafted silica particles was increased to33.5and348C when NV values were3 and4.In the current results,it is con?rmed that the surfaces of silica particles are successfully grafted by PNIPAm polymer.
3.2.Preparation of hybrid silica particles encapsulating PNIPAm polymer
To prepare the hybrid particles,?rst of all,it is important to synthesize precursor.NIPAm–VTMS complex monomers were synthesized by the reaction of NIPAm with VTMS in the presence of KPS and MBA as shown in Fig.8.The reaction took place between a vinyl group of NIPAm and VTMS as a co-polymerization.
Fig.9shows the typical SEM and TEM images of the hybrid spheres prepared with PNIPAm as a core material and silica as a shell material at408C.The diameters of the hybrid spheres are shown in Fig.9A and B to a range of250nm mean diameter.
To con?rm the core–shell structure of hybrid materials,the particles were calcined at6008C for5h.Through the calcination step,PNIPAm polymer of the hybrid particle can be effectively decomposed and eventually removed.However,inorganic materi-als are not affected by the high temperature and the silica materials are remained as the hollow structure.Their TEM images show the lighter center portion and the darker edge,which further con?rms their hollow structure(Fig.10).It can be clearly seen from the images that the silica shells are symmetric and uniform with a thickness range of20nm.
Moreover,when the amount of NIPAm–VTMS precursor was doubled,the obtained hybrid particles exhibited a spherical structure with diameter of about400nm observed by scanning electron microscopy(SEM)and transmission electron microscopy (TEM)(Fig.11).The size distribution of hybrid particles increases with increasing concentration of NIPAm–VTMS precursor from 1wt%(Fig.9)to2wt%(Fig.11).Generally,the concentration of NIPAm–VTMS precursor in?uences the concentration of nuclei particles in the reaction system.After the addition of ammonia hydroxide,primary hybrid particles are prepared through the nucleation step.Then,poly-condensation of primary
particles Fig.11.SEM(A)and TEM(B)images of hybrid particles encapsulating PNIPAm
polymer.Fig.12.TEM images of the hollow shape after calcination process.
Y.-G.Lee et al./Journal of Industrial and Engineering Chemistry18(2012)744–751749
resulted in the larger secondary particles of sub-micron sizes.This process continues until precursors or nuclei particles are fully consumed or until the reaction system is stable.Eventually,at this condition,the high concentration of NIPAm–VTMS precursor leads to the extension of growth step and the longer growth process that causes the increase of particle size [25].As a result,the experiment indicates that the morphology and size of the hybrid spheres are dependent upon the concentration of the NIPAm–VTMS precursor.
Similar to the PNIPAm silica hybrid materials,which was made using a NIPAm–VTMS precursor (Fig.10),the hollow structure of particles was also identi?ed when the addition of precursor concentration was increased as shown in Fig.12.After calcination process at 6008C for 6h with particles,all solid hybrid spheres were converted into well-de?ned hollow shape.The shell thickness was estimated from images to be approximately 30nm.
The simultaneous TGA traces for hybrid particles synthesized by the polymerization of NIPAm with VTMS are shown in Fig.13.The ?rst area is a below 3008C with a minimum at 1008C that can be attributed to the combined loss of water and residual organics from the preparation.This area occurs concurrently with a TG weight loss of 5%.The second area,a very sharp decrease ranging from 300to 4508C,may be due to the degradation of the PNIPAm polymer and corresponds to the weight loss of about 30%.
FT-IR spectroscopy was used to characterize the structure of samples (Figs.9and 11)that are shown in Fig.14.Bands located at each peaks are associated with the silica materials and PNIPAm polymer,which are similar to Fig.6.From the IR data,it is assumed that PNIPAm encapsulated hybrid silica spheres are synthesized well.
4.Conclusions
In summary,two types of PNIPAm/silica hybrid particles were prepared in aqueous solution.In the ?rst type of hybrid materials,which are consisted of silica core with PNIPAm shell structure,it was discovered that well-de?ned polymer chain were grown from the VTMS particles surfaces to yield individual particles composed of a silica core and a well-de?ned,densely grafted outer PNIPAm layer.Interestingly,in our study,the thickness of PNIPAm polymer on the silica surface could be controlled by changing the concentration of NIPAm monomers in solution.In the second type of hybrid nano colloids,which are prepared by NIPAm–VTMS monomer,it was found that PNIPAm polymer encapsulated silica hybrid particles exhibit the core/shell structure.Most of the colloidal composites were comprised of approximately spherical particles with relatively narrow size distributions.These results suggest that the strategy of using a polymer with silica spheres could be led to new nanodevices for unique thermal sensitive controlled release and circulation properties in different solution environments.
Acknowledgement
This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF)grant funded from the Ministry of Education,Science and Technology (MEST)of Korea for the Center for Next Generation Dye-sensitized Solar Cells (No.2010-0001842).
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雅思口语素材汇总之端午节 雅思口语素材:Dragon Boat Festival(端午节) Qu Yuan The Dragon Boat Festival, also called the Duanwu Festival, is celebrated on the fifth day of the fifth month according to the Chinese calendar. For thousands of years, the festival has been marked by eating zong zi (glutinous rice(糯米)wrapped to form a pyramid using bamboo or reed leaves) and racing dragon boats. The festival is best known for its dragon-boat races, especially in the southern provinces where there are many rivers and lakes. This regatta(赛舟会)commemorates the death of Qu Yuan , an honest minister who is said to have committed suicide by drowning himself in a river. Qu was a minister of the State of Chu situated in present-day Hunan and Hubei provinces, during the Warring States Period (475-221BC)(战国时期). He was upright, loyal and highly esteemed for his wise counsel that brought peace and prosperity to the state. However, when a dishonest and corrupt prince vilified Qu, he was disgraced and dismissed from office. Realizing that the country was now in the hands of evil and corrupt officials, Qu grabbed a large stone and leapt into the Miluo River on the fifth day of the fifth month. Nearby fishermen rushed over to try and save him but were unable to even recover his body. Thereafter, the state declined and was eventually conquered by the State of Qin. The people of Chu who mourned the death of Qu threw rice into the river to feed his ghost every year on the fifth day of the fifth month. But one year, the spirit of Qu appeared and told the mourners that a huge reptile(爬行动物)in the river had stolen the rice. The spirit then advised them to wrap the rice in silk and bind it with five different-colored threads before tossing it into the river. During the Duanwu Festival, a glutinous rice pudding called zong zi is eaten to symbolize the rice offerings to Qu. Ingredients such as beans, lotus seeds(莲子), chestnuts(栗子), pork fat and the golden yolk of a salted duck egg are often
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雅思口语素材 Document serial number【LGGKGB-LGG98YT-LGGT8CB-LGUT-
Useful Expressions: Words and phrases Friends and communication: solidify/ strengthen/ enhance/ promote communication / connection with mutual understanding relationship network/circle of f r i e n d s cultivate/develop friendship with s b . keep steady relationship with sb. establish interpersonal networksac build up the social circle spur message transmission Knowledge and experience widen one’s outlook broaden one’s vision/horizon acquire knowledge and skills comprehensive/overall quality
expand/enlarge one’s scope of knowledge knowledge reserve/base/storage theoretical knowledge practical skills social experience broaden one’s knowledge base promote one’s overall/ comprehensive competence accumulate experiences learn lessons from past experiences Work and experience the scarcity of employment o p p o r t u n i t i lay the foundations for career p r o s p e r i t y
U s e f u l E x p r e s s i o n s: Words and phrases Friends and communication: mutual understanding solidify/ strengthen/ enhance/ promote communication / connection with relationship network/circle of friends cultivate/develop friendship with sb. keep steady relationship with sb. establish interpersonal networksac build up the social circle spur message transmission Knowledge and experience widen one’s outlook broaden one’s vision/horizon acquire knowledge and skills comprehensive/overall quality expand/enlarge one’s scope of knowledge knowledge reserve/base/storage theoretical knowledge practical skills social experience broaden one’s knowledge base promote one’s overall/ comprehensive accumulate experiences competence learn lessons from past experiences Work and experience the scarcity of employment opportunities lay the foundations for career prosperity immerse oneself in endless job tasks boost/augment/enhance efficiency be adept in boost one’s c ompetitiveness Health and pressure diminish individuals' leisure time drive away lassitude lighten one’s burden homework/workforce overload
近期雅思口语卡片新题素材汇总 人物Describe a classmate of yours Describe a good friend Describe a happy person Describe a colleague Describe a neighbor Describe your own personality Describe a family member Describe a child you know Describe an old person Describe an old person who has influenced you the most Describe a successful person Describe a singer Describe a sportsman Describe a movie star Describe a character in TV or movie Describe a teacher of yours Describe a famous person that you want to spend a day with.地点Describe a building at schools Describe a historical place
Describe a monument Describe an interesting building Describe a lake, river or sea. Describe a peaceful place Describe a leisure place Describe a park Describe a place of interest Describe a natural beauty Describe a city you want to live in Describe a place you have visited Describe a place you always go for shopping
一.雅思P2相关话题 一日假期 和外国朋友一起吃饺子的建议 1.The best way to eat a dumpling is in one bite. “Dumplings are designed to be consumed in one mouthful, as it’s the best way to enjoy the combination of the meat filling and the very thin and springy flour wrapper,” If you can’t use chopsticks, eat your dumplings with your fingers. Avoid using a fork at all costs, as piercing the dumpling will compromise the flavour. 3.Mix two parts vinegar with one part soy sauce for the perfect dumpling sauce. Add young ginger slices too， Chili oil is also a great addition when available. 4.Dumplings are just one element of dim sum. “Dim sum doesn’t just include dumplings. It’s also braised dishes like pork ribs, chicken feet, and beef balls. It’s actually small tapas-style dishes that are eaten in Cantonese restaurants at lunchtime,” 5.Xiao long bao dumplings are different from others as they contain broth. They originated in the Jiangnan region of China and are prepared in bamboo steaming baskets called xiao long, hence the name. 6.When eating xiao long bao or a dumpling with a ~soupy~ interior, opt for chopsticks and a spoon. “As soon as the dumplings arrive at your table, lift one from the steamer basket onto a soup spoon. Next, tear the skin of the dumpling by pressing the chopsticks from the side of the dumpling onto the spoon. The broth will ooze out onto the spoon. Sip the soup then enjoy the dumpling in one mouthful.” 7.You can tell whether your dumpling was cooked fresh or frozen by looking at the skin. “The skin of a freshly made dumpling is springy and light. “Frozen ones tend to be soggy.” 8.When makingdumplingsat home, try to keep your packages small.
雅思口语素材训练 by Tina Li Do you like music??A—肯定:Definitely yes, everyone enjoys music, and I am no exception! I love... 否定 :Well, honestly speaking, music is really not my cup of tea, simply because... ( 给出直接原因) What—pop, techno ( 电音音乐), hip-hop, rock, meditation ( 冥想乐) and especially light music.( 罗列名词) Where—Normally speaking, I would like to listen to music with my earphones when I take a ride on public transportation. ( 给出一个具体的场景) When—As long as I couldn’t go to sleep, I’d like to listen to some light music to calm myself down. ( 给出一个条件 :As long as I..., I would...)
Who—My most favourite singers include Adele, James Blunt, Avril Lavigne, and so forth. ( 喜欢的歌手) Why—I am fond of music mainly because it can cheer me up greatly when I feel down/low/ blue/bored/tired/depressed. ( 心情不好的时候让我高兴起来)?Besides, I also believe that music is an indispensable part of culture and tradition, through which I could have a better understanding of different cultures around the world, including cowboy culture, African-American street culture, the three main reli- gions and so on. ( 有助于理解不同的文化) Do you like watching movies?? A—Speaking of movies, yes, I am a big fan of all types of movies, such as...?What—comedy, action, romance, sci-fi, manga, vampire, zombie, animation...
做有偿工作的人 Describe a person you know who is doing a paid job. You should say: Who this person is What job it is; How long the job lasted; And explain why you or this person chose to do this job. 让你笑的小孩 Describe a time that a child did something that made you laugh. You should say: When this happened Who the child was What the child did And explain why it was funny 特殊的旅行 Describe an educational trip you went on when you were in school. You should say: When and where you went; Who you went with; What you did; And explain what you learned on this trip.
Describe an electronic machine you want to buy. You should say: What it is When you know this machine What specific And explain why you want this machine 难忘的广告 Describe an unforgettable advertisement (that you saw or heard liked) You should say: Where you saw or heard it What kind of advertisement it was What the contents of the advertisement were (or, what product or service was advertised) And explain how you felt when you saw or heard this advertisement/why you like it
【2019-2020】雅思口语话题素材-精选word文档 本文部分内容来自网络整理，本司不为其真实性负责，如有异议或侵权请及时联系，本司将立即删除！ == 本文为word格式，下载后可方便编辑和修改！ == 雅思口语话题素材 雅思口语素材总结雅思口语要求学生平时多多的积累素材，在口语方面要不断的加强练习。烤鸭们要多模拟不同的场景，多用丰富的口语短语，这 样你的雅思口语水平才能越来越高。下面是常用的一些口语短语，供大家参考！ 1、 a change of pace 改变步调;换口味 You cant do these chemistry experiments all day long . You certainly need a change of pace . 2、 a far cry from 相距甚远 The published book is a far cry from the early manuscript . 3、 and how 的确 A ： Shes a good dancer . B ： And how . 4、 a matter of time 时间问题 It is only a matter of time . 5、 a phone call away 一个电话之远，即愿意过来帮忙 If you need my help , do let me know . Just remember I am a phone call away . 6、 a while back 不久以前 Well , I listened to that CD you lent me a while back . 7、 all along 一直 I knew it all along . 8、 anything but 绝对不 I was anything but happy about going . 9、 account for 解释 How do you account for it ? 10、 after all 毕竟;终究 A ： Ive just seen the X - rays and your teeth look just fine . B ： I see . Then there is nothing to worry about after all . 11、allergic to 对过敏 Oh man ! Something in this room is making my eyes itch . I must be allergic to something . 12、 at sbs service 愿为某人服务 I am at your service at any time . 13、 around the clock 24小时不停 Martha studied around the clock for management exam . 14、 as far as I know 就我所知 But as far as I know , he once won the world champion at the Olympic Games . 15、 at home with 对很熟悉 She is at home with problems like this . 16、 back out 退出 A ： Wasnt Bert supposed to sing tonight ? B ： Yes , but he backed out at last minute . 17、be cut out for 适合于，有做某事物的天赋 She is cut out for a dancer . 18、 be absorbed in 全神贯注于某事物 She has been absorbed in a horrorfiction . I cant tear her away . 19、 be addicted to 对某事物上瘾 She has been addicted to drugs for years . 20、 be attached to 对某事物有感情 A ： Im amazed that you are still driving that old car of yours . I thought you would have gotten rid of it years ago . B ： It runs well and Ive actually been quite attached to it .
雅思口语雅思托福技巧雅思口语-美联国际教育雅思口语话题素材积累：Hometown 2014-02-18 17:00 类别：雅思口语来源：enguo 责编：meten 考生们在练习备考雅思口语过程中，可以多从身边的生活中取材，锻炼自己的口语表达能力。下面小编就为大家整理了雅思口语话题素材：Hometown，希望对大家备考有所帮助。 1、Where do you come from? 2、What tourist attractions are there in your hometown? Would a foreign visitor enjoy them? 3、Did you learn much about the history of your hometown in school? 4、What do you think needs to change in your hometown? 5、What place(s) in your hometown do you go to in your spare time? 6、Why did you choose to live here/there? 7、What do you like about your hometown? 8、What do you think needs to be done to make your hometown a better place to live in? 9、For you, what benefits are there to living in a big city? 10、What facilities does your hometown have? 11、What sorts of buildings are there in your hometown? 12、What's the most attractive part of your hometown? 13、What forms of transport do visitors use to come to your hometown? 14、How could your hometown attract more visitors? 15、Has the weather in your hometown changed much in recent years? Important: At the moment (2012) in China, there are about 30 different topics being used in Part 1. These topics and questions are in the examiner's question book(topic pool), the examiner is not allowed to make his or her own questions in Part 1 test. 众所周知，雅思口语考试是非常重视临场发挥的，虽然这些雅思口语考试试题看上去都很平常，但是还是要求大家在自己熟悉的题目和熟悉的事物中发挥自己的真实水平，所以大家一定不能掉以轻心，平时就要多加训练，在考场上正常甚至超常发挥出来。
雅思口语高分模板汇总 多看一些雅思口语高分模板，有助于提升英语说话的逻辑，还能增强我们遣词造句的能力。下面就和大家分享，来欣赏一下吧。 雅思口语高分模板：描述兴趣爱好的话题 雅思口语高分模板一： From a middle class family, I was born in Hsin Ying, Tainan on October 10th, 1965. My father is a civil official at Tainan City Government. My mother is a house wife good at . Although I am the only child of my parents, I am by no mans a spoiled one. On the contrary, I have been expected to be . I study hard at school. Besides texts knowledge, journalism is my favorite; whenever reading, my heart is filled with great joy and interesting. 从中产阶级家庭，我出生在Hsin Ying，台南1965年10月10日。我父亲是台南市政府的一名公务员。我母亲是一位善于烹饪的家庭主妇。虽然我是我父母的独生子女，但我决不是一个被宠坏的孩子。相反，我被认为是一个成功的受过高等教育的人。我在学校努力学习。除了文字知识，新闻是我的最爱;每当阅读，我心中充满了极大的乐趣和乐趣。
雅思口语试题参考素材 1.被污染的地方 Last vacation, I went to Hainan with my family.Hainan is such a wonderful place that I will never forget it. It's really a good place where gave me a rather good impression. I feel so wonderful during the journey, as I have experienced a lot of things for the first time. The sky is also brighter and clearer than that I had ever seen. It was my first time to experience the sea and the beach in the sunshine. When sitting on the cruise, I could clearly see the ocean waves pushing the windows of the cruise. But last week, I went to Hainan again. I went to the beach the second time, but this trip changed my idea about its scenery. There were a lot of rubbish. The water was full of flotsam and refuse.When I walked along the sea, terrible smell went into my nose.The beach had been affected by pollution.Due to poor management, people who visited there damaged the environment. It is to be regretted that a beautiful place has gone.
描述一个未来你想安家的地方。 This place is a coastal mountain in Hong Kong, I have been there followed a tour group last winter vacation.The mountain is not high, but it is arborous.And when you walk in the mountain,you will find the air is particularly fresh. The sky way stretching from the foot of the mountain to the peak , and there are many apartment buildings and villas in there. Down from the mountain is the ocean, it has soft beach as well as clear seawater,sea birds flying overhead time to time. The inhabitants of the mountain exercise along the highway by running or cycling every morning. I am aspire to live in that place because it isvery comfortable. In addition to the good environment , another reason I choose to make a home there is that, Hong Kong is an international metropolis, and there are a lot of employment opportunities, I think I can find a nice job there. And Hong Kong are referred to as the shopping paradise, the stuff is superior in quality and the price is relatively cheap. But in Hong Kong, people have a rapid pace of life, I think I can’t adapt to the fast pace of life. So living in the mountain far away from the downtown is a good choice for me because I can go to work in downtown during the day, and go back to the mountain to release the pressure of a day at night. In addition,the traffic is very developed in Hong Kong, so there is no need to worry about the traffic, I can arrive quickly at the downtown if i want. 我喜欢的一个喜剧演员是马特·勒布朗，他在情景喜剧《老友记》中饰演乔伊·崔比安尼。剧中乔伊与钱德勒为共租公寓的室友，是一位没什么天分但很执着的龙套演员，他从没有拍过什么很重要的角色，但是对于每一个上镜机会他都非常珍惜，非常认真。在拍戏方面的每一点进步都会让他非常兴奋。我觉得他是《六人行》里最单纯最可爱的一个人，他四肢发达、头脑简单，他的很多台词都非常搞笑，动作也很滑稽。另外乔伊是一个非常善良，富有爱心的人，他非常关心他的五个朋友，总能给人带去温暖。马特真的把这个演员演活了。从乔伊身上我们能看到自己的影子，虽然我们都是平凡的普通人，但是为了自己的梦想一直在努力，就算遇到很多挫折依然很乐观。我觉得这是马特塑造的这个角色最成功的地方，它能给人带去希望。 One of my favorite comedian is Matt Leblanc, he played in the situation come dy Friends,which i watched a couple years ago,he played in friends as the cha racter,Joey Tribbiani . In Friends ,joey is an actor, an utility man.Although he had never took a chance to play a big role,he cherish every chance he got.An d with one hundred percent of the effort.Every bit of progress in performance would make him very excited. I think he is a simple person as well as the most lovely one in Friends.he is limbs developed but simple-minded, and many of his lines are very funny, actionsare also very funny, Matt just make the ch