聚(丙烯酸-co-甲氧基聚乙二醇甲基丙烯酸酯)梳状高分子的侧链结晶行为

STUDIES ON CRYSTALLIZATION BEHAVIOR OF SIDE CHAINS OF POLY(ACRYLIC ACID-co-METHOXYPOLYETHYLENE GLYCOL MONOMETHACRYLATE) COMB-LIKE POLYMERS

以不同分子量的甲氧基聚乙二醇甲基丙烯酸酯(mPEG1000MA或mPEG2000MA)为大单体,与丙烯酸(AA)、甲基烯丙基磺酸钠(SMAS)等单体通过自由基聚合反应合成了一系列具有不同分子量、不同侧链长度、不同侧链密度的聚(丙烯酸-co-甲氧基聚乙二醇甲基丙烯酸酯)梳状高分子.用乌氏黏度计测定梳状高分子的特性黏数以表征其分子量大小.采用示差扫描量热法(DSC)测量梳状高分子中甲氧基聚乙二醇(mPEG)侧链的结晶温度和熔点.分析认为,当mPEG1000MA与AA共聚后,处于玻璃态的PAA主链对mPEG侧链的物理限制作用很大程度上影响了mPEG侧链的结晶行为.这种在受限环境中mPEG的结晶温度和结晶熔点均发生明显漂移,低于PEG在本体中的结晶.结晶温度和熔点的偏移受到主链长度、侧链疏密、侧链长度、磺酸侧基含量等诸多分子结构和组成因素的影响.研究结果表明:共聚物中侧链越稀疏,侧链结晶受限作用越明显;mPEG侧链分子量越大,其结晶受到主链的限制作用越弱;在梳状高分子主链上引入磺酸侧基官能团后,侧链的结晶的受限程度增加,并且由于非晶侧链的增多,表现出明显的侧链玻璃化转变.

A series of water-soluble comb-like copolymers of poly（acrylic acid-comethoxypolyethylene glycol monomethacrylate）（（P（AA-co-mPEGMA））） with different compositions and structures were synthesized by free-radical copolymerization of acrylic acid and methoxypolyethylene glycol monomethacrylate（mPEG1000MA） or mPEG2000MA macromonomers,sodium methyl allyl sulfonate（SMAS） in aqueous solutions.The intrinsic viscosity of comb-like P（AA-co-mPEGMA） copolymers,measured by using Ubbelohde viscometer,was used as a factor to characterize the molecular weight.Crystallization behavior of the mPEG side chains in comb-like copolymers was studied by DSC that allowed accurately measuring melting point,crystallization temperature as well as melting enthalpy.The results indicated that the crystallization of the mPEG side chains proceeded under a confined condition created by the glassy PAA main chains.It was shown that the melting point,crystallization temperature and melting enthalpy of mPEG side chains were different from those of the pure PEG chains and were significantly affected by many structural factors such as the side chain density,side chain length and main chain length etc.