Fluorinated ABC Triblock Terpolymers: Effects of Flexible and Rigid Hydrophobic Moieties
Sen Li, Jinlin He*（何金林）, Mingzu Zhang, Hairong Wang and Peihong Ni*（倪沛红）
College of Chemistry, Chemical Engineering and Materials Science，State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials，Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis，Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, Soochow University
POLYMER CHEMISTRY ,2016,卷: 7 ,期: 9 ,页: 1773-1781
This paper is aimed at comparing the effects of flexible and rigid blocks on the morphologies of multi-compartment aggregates self-assembled from two kinds of fluorinated ABC triblock terpolymers, in which polyisobutylene (PIB) with a low glass transition temperature (T-g similar to -67 degrees C) and polystyrene (PS) with high T-g (similar to 100 degrees C) were selected as the flexible and rigid blocks, respectively. The fluorinated triblock terpolymers (abbreviated as PIB-b-PDMAEMA-b-POFPMA and PS-b-PDMAEMA-b-POFPMA, respectively) with similar relative block lengths were synthesized via consecutive oxyanion-initiated polymerization (OIP) of 2-N, N-(dimethylamino) ethyl methacrylate (DMAEMA) and 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate (OFPMA) using pre-functionalized PIB-O-K+ or PS-O-K+ as the macroinitiators. These terpolymers could self-assemble in aqueous solution since the PDMAEMA block is hydrophilic, PIB and PS blocks are hydrophobic, while the POFPMA block is both hydrophobic and lipophobic. The self-assembly behavior was analyzed by transmission electron microscopy (TEM). It has been demonstrated that PIB-b-PDMAEMA-b-POFPMA with the flexible PIB block could self-assemble into four types of reproducible nanostructures with the increase of polymer concentrations, including multicompartment micelles, fiber-like aggregates, nanotubules and rod-like aggregates. More interestingly, a uniform zig-zag pattern was observed on the surface of these rod-like aggregates after the solution was maintained without stirring for one week. In contrast, for the PS-b-PDMAEMA-b-POFPMA system containing a rigid PS block, the similar morphologies were rarely observed, except for spherical, hamburger and flower-like multicompartment nanostructures. The present work reveals that the flexibility or rigidity of the hydrophobic segment as well as the polymer concentration exerts a big influence on both the self-assembly behavior and formation of diversified morphologies.
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