聚合物纳米胶囊制备新方法——RAFT细乳液界面聚合

聚合物纳米胶囊制备新方法——RAFT细乳液界面聚合

浙江大学博士论文摘要

高到0．94。这些结果验证了均相成核机理，聚合动力学、液滴／乳胶粒粒径分布、分

子量分布的结果也支持了均相成核机理。

3)实验还发现用油溶性引发剂(AIBN)代替水溶性引发剂(KPS)，引入水相自由基捕捉剂(NaN02)都可以减少体系发生均相成核，提高了合成纳米胶囊的选择性。

二、在以上机理研究的基础上，论文开展了纳米胶囊的结构调控研究。针对以St 为

单体，ND为核芯材料，poly(MAAl6．CO．St7)RAFT为RAFT试剂，在pH值为6．45

下的RAFT界面细乳液聚合，研究了RAFT试剂用量对合成纳米胶囊的粒径影响，制

备得到了直径在112～480 nm范围内的纳米胶囊；针对以St为单体，HD为核芯材料，

poly(AA2-b—St2)RAFT为RAFT试剂，在pH值为8．3下的RAFT细乳液界面聚合，考

察了后补加小分子乳化剂SDS对合成纳米胶囊的粒径分布影响，经离心分离制备得到

了形态粒径分布均一的纳米胶囊，直径约为112 nlll，粒径的差异分布系数(CV)为5．4％，壳厚约为20 nm；研究了St／ND用量比对合成纳米胶囊的核壳重量比影响，制

备得到了(ND／PS)为1／4至1／1的纳米胶囊。当进一步减少St用量，设计核壳比

为 211时，聚合物壳层变得较薄，强度不够，胶囊出现塌陷现象；研究了交联剂对

合成纳米胶囊的壳层强度影响，制备得到了高交联密度聚合物壳层的纳米胶囊，甚至

整个聚合物壳层为交联剂均聚物，其强度得到大大提高，进一步用溶剂洗脱除去核芯材

料制得了“中空”纳米胶囊。

三、将RAFT细乳液界面聚合制备纳米胶囊技术拓展到反相细乳液聚合中，合成了

PNIPAM包裹Na2S04的温敏响应性纳米胶囊，直径为100～250 nin之间，壳层厚度约

为30 nna。

关键词：RAFT，界面聚合，细乳液聚合，反相细乳液聚合，纳米胶囊。

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浙江大学博士论文 Abstract

Abstract

(Hollow)Nanocapsules have shown highly promising applications in a large variety of

fields due to the special nanostructures ．

RAFT(Reversible Addition ／Fragmentation

Transfer)interfacial miniemulsion polymerization offers a

straightforward method

to

synthesize nanocapsules ．Based on the self-assembly of amphiphilic macro —RAFT agents

on the interface of droplets ／water

and the radical

polymerization was confined

on the

interface ，a polymeric

shell was in-situ formed ．This method was not only able to precisely control the structures of nanocapsules ．but also offerred such advantages as a simple and environmental process ，which is highly efficient ，easily scale·up．In principle ， this method should

offer a generally robust way to synthesize naocapsule ，but lots of solid

particles were found in many experimental studies ，of

which the mechanism was not clear yet ．In the current thesis ，the formation mechanism of the solid particles accompanying the nanocapsules was investigated ，aiming at developing RAFT interfacial miniemulsion

polymerization as a versatile facile way to synthesize nanocapsules of high selectivity ．

The following

results were achieved ：

(1)．The formation mechanism of the solid particles was proposed that some of the

amphiphilic oligomer radicals(Amphi —R ．)，which were formed from the reaction of

macro-RAFT agent

anchored on the interface of droplets with the primary

radicals ，would

desorbed into the water phase ．Since it took longer time for the radicals(Amphi-R 。)to re·-enter into the droplets than those water·-phase radicals in the conventional (mini)emulsion

polymerization ，the Amphi —R ．would induce the homogenuous nucleation ， leading to the

formation of the solid particles ． Based

on

the RAFT interfacial miniemulsion ，the

equations of estimating the

feature time of the chain radical for addition ／

precipitation(tp)in water phase and the feature time of radica entry into the

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