D-O-008-分散聚合法制备高交联单分散聚(甲基丙烯酸甲酯-乙二醇二(甲基丙烯酸)酯)微球-佟斌
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EGDM/(MMA+EGDM)(wt%) Dn(μm)
PDI
CD/wt% Yield/wt% T*5%/oC
15
3.4
1.106
82.1
9.5
--
25
2.3
1.097
85.6
26.5
268
50
2.1
1.094
90.9
42.5
257
75
1.8
1.085
93.1
61.0
252
100
1.4
1.077
98.4
本文选用甲醇为分散介质,采用分散聚合的方法制备了高交联度的甲基丙烯 酸甲酯(MMA)/二甲基丙烯酸乙二醇酯(EGDM)的共聚单分散微球。
实验部分
化学试剂、提纯方法、产物后处理及表征见文献[7]。微球制备的典型程序:在 三口烧瓶中加入单体、交联剂、引发剂、稳定剂和分散介质,搅拌均匀,待体系 透明后,通氮气。开始,烧杯悬置在水浴上,待加热水浴达到设定温度(56℃) 时,关小氮气,调节搅拌转速为 60~110rpm,再快速升上水浴,开始加热反应。 反应在恒定温度、氮气保护下进行。反应时间 10h。表 1 是交联聚合物微球制备的 标准配方,如无特殊说明均按此配方投料。
表 2 是在单体 MMA 和交联剂 EGDM 的总量保持不变的情况下,改变两者之间的
比例,获得的聚合物微球的性能参数。图 1 是交联剂浓度为 50wt%获得的聚合物
微球的扫描电镜照片。由表 2 可知,在交联剂和单体总量不变时,当单体量加大,
微球的粒径也随着变大,但是分散性变差;也就是当 MMA/EGDM 的比值变大时,
Preparation of monodisperse highly crosslinked poly(methyl methacrylate-ethylene glycol dimethacrylate) microspheres by
dispersion polymerization
TONG Bin1, SUN Hongbo1, CAO Moli1, DONG Yuping1, ZHI Junge2 1.School of Materials Science and Engineering, Beijing Institute of Technology, Beijing,
球径变大,分散性变差。这是因为,当反应物中交联剂的比例增大时,在成核期,
形成交联结构,从而使分子链更容易从溶液中析出,从而使微球的粒径变小,而
且在形成高交联的球体后,反应物也不容易扩散到球的内部,而只能在球的表面
反应,也不利于球径的增加,因此,随着交联剂的用量的增大,球径会逐渐减小。
又因为交联剂的反应活性比单体高,能更快的引发反应,所以,在反应的初期就
已经大量聚合,令成核期缩短,并随着单体的减少,二次成核的几率也降低,使
粒径分布更趋向单分散。
以氯仿为溶剂,对聚合物微球索氏抽提 12h,抽提后与抽提前质量的比值定义
为交联度。结果表明:交联度 CD 随交联剂浓度的增加而增加,当交联剂浓度为 100%
时,交联度为 98.4%,索氏抽提后的质量损失仅为 1.6%。从热失重曲线(图 2)
research about the preparation of crosslinked microspheres by dispersion polymerization, but the crosslinker concentration were less than 5 wt % relative to the monomer. When crosslinker concentration continued to be increased, odd-shaped particles were obtained with a broad size distribution or coagulation of the dispersion was resulted. In this paper, highly crosslinked P(MMA-EGDM) microspheres were prepared by dispersion polymerization in methanol. The effect of different ratios of MMA and EGDM on polymerization were investigated. The results showed that: when the concentration of MMA was lower than 2wt%, the reaction can go through, and the crosslinked degree of obtained microspheres was higher than 82%. The obtained microspheres have good thermal stability. Key words:Dispersion polymerization,Microsphere,Highly crosslinked
分散聚合法制备高交联单分散聚(甲基丙烯酸甲酯-乙二醇二 (甲基丙烯酸)酯)微球
佟斌 1,孙洪波 1,曹茉莉 1,董宇平 1,支俊格 2
1 北京理工大学材料科学与工程学院,北京 100081 2 北京理工大学理学院化学系,北京 100081
关键词 分散聚合 聚合物微球 高交联
自 1955 年美国里海大学乳液聚合物研究所 Vanderhoff 和 Brodford 公布他们 制备高度均一粒径的聚苯乙烯微球的方法[1]以来,聚合物微球已经成为一个新的研 究领域 [2]。由于分散聚合法对粒径的控制容易,体系组成简单,制备的微球的粒 径分布好,成为目前制备几到几十微米微球的主要方法[3,4]。Stover 等人[5]通过沉 淀聚合的方法制备了不同交联剂浓度的聚合物微球。黄文强等人[6]采用蒸馏-沉淀 聚合获得了单一分散的聚二乙烯苯微球。通过分散聚合也可以获得交联型的聚合 物微球,但相对于单体的交联剂浓度低于 5wt%,当交联剂浓度进一步提高时,得到 的聚合物微球表面粗糙,或聚合体系不稳定出现絮凝使反应无法进行下去。
可以看出高交联的聚合物微球具有很好的热稳定性,质量损失 5%的热分解温度在
250oC 以上。体系中其它因素的影响作用以及聚合机理有待于进一步考察。
Table 2. The effect of different ratio of MMA and EGDM in the feed on the poymerization
100
200
300
400
500
Temperature/℃
Figure2. The thermogravimetry curves of different crosslinker concentrations
参考文献:
[1]Vanderhoff J W, Brandford E B. Polymer Colloid I (Fitch R M Ed), New York: Plenum Press, 1971. [2]Kawaguchi H. Prog Polym Sci, 2000,25:1171. [3]Jeffrey S. D., Randy S. F., Li W. H., Stover D. H., Macromolecules, 1999,32:2838-2844. [4]齐东来,杨新林,黄文强。离子交换与吸附, 2005, 21(6):481 ~ 486。 [5]Li W. H., STOVER HARALD D.H., Journal of Polymer Science: Part A: Polymer Chemistry, 1999, 37:2899–2907. [6] Bai F., Yang X. L., Huang W. Q.,Macromolecules, 2004, 37: 9746. [7]佟斌,孙洪波,石建兵,曹茉莉,董宇平,支俊格。北京理工大学学报,2007,27(3): 270-273
100081; 2.School of Science, Beijing Institute of Technology, Beijing, 100081 Abstract:Dispersion polymerization process is simple, just in a single batch and the obtained microspheres are monodisperse under favorable circumstances. Up to now, highly crosslinked microspheres could be obtained mainly by precipitation polymerization and distillation-precipitation polymerization. There are also much
Table 1.Standard recipe for the preparation of crosslinked PMMA
Materials
Weight/g
monomer
MMA
1.0
cross-linker
EDGM
1.0
initiator
AIBN
0.3
stabilizer
PVP
1.0
medium
57.0
250
*the temperature of 5% weight loss
Figure1. SEM micrograph of P(MMA-EGDM) microsphere with
50wt% crosslinker
Residual/%
100 80 60 40 20 0 0