Synthesis And Structures Of Reactive Comblike Copolymers And Their Applications As The Compatibilizers For Immiscible Polymer Belnds

Facile constructions of complex macromolecular architectures such as star-like, hyper-branched, dendritic and comb-like copolymers have attracted great attentions due to their branched topologies, unique physicochemical properties and widely applications. As a subclass of graft copolymers, comb-like copolymers comprising regular side chains have captured great interests for their easiness of synthesis and their applications as polymer electrolytes, thermoplastic elastomers and smart biomaterials, etc. Herein, we described the facile synthesis of a novel reactive comb copolymer (RC) by a "Grafting through" method; copolymerizations of methyl methacrylate (MMA), glycidyl methacrylate (GMA) and MMA macromer afforded a comblike copolymer, which had regular PMMA side chains and epoxide groups, randomly distributed along the backbone. The RC copolymers were appplied as compatibilizers in immiscible polymer blends. The epoxide groups of RC copolymers was able to react with the carboxyl or hydroxyl groups of a series of engineering plastics, such as poly(L-lactic acid) (PLLA), polycarbonate (PC), poly(ethylene terephthalate) (PET); thus, a "double comblike" copolymers were obtained, with the PMMA side chains interacted with one phase and the grafted chains interacted with the other phase. It was anticipated that this novel kind of RC copolymers would have much higher compatililizing efficiency.This thesis was divided into three main parts:1. Synthesis of RC: Firstly, pre-macromer (PMMA-COOH) was synthesized via a telomerization of MMA with thioglycolic acid (TAC) as a chain transfer agent and 4,4’-azobis (4cyanovaleric acid) (ACVA) as an initiator. The molecular weight of PMMA-COOH could be controlled precisely by the variations of reacting condition and feed ratios. Then MMA macromer was obtained by a nucleophilic ring-opening addition between the terminal carboxyl groups of PMMA-COOH and epoxide groups of GMA. By copolymerizing MMA macromer with MMA and GMA, a RC copolymer was obtained; without the using of macromer, we obtained a reactive linear (RL) copolymer.2. Investigations on the thermal behaviors of RC: The molecular architechture effects on the thermal behaviors of RC have been systematically investigated. The main results are as follows. Firstly, the TGA results indicated that the thermal stability could be improved by introducing ethyl acrylate (EA) into the backbone, increasing the length of the backbone and decreasing the content of GMA; the existence of side chains also had positive impacts on thermal stability. Secondly, from DSC data, all RC copolymers exhibited two distinct transitions at about 116℃ and -20℃, while linear copolymers and commercial PMMA showed only one glass transition temperature corresponding to the relaxation of the main chain, which confirmed the existence of the PMMA side chains. Finally, from DMA data, the activation energy for P transition of the RC copolymers decreased with the incorporation of long side chains, which was attributed to the increased free volumes for the comb-like structures.3. The molecular architecture effects on compatilizing efficiency for several immiscible polymer blends:RC or RL copolymers with different topological structures have been used to improve the compatibility of three typical immiscible polymer blends: poly(L-lactic acid)/poly vinylidene fluoride (PLLA/PVDF), Acrylonitrile Butadiene Styrene /poly(ethylene terephthalate) (ABS/PET), poly(L-lactic acid)/polycarbonate (PLLA/PC). Compared to their linear counterparts, RC coplymers exhibited much higher compatibilization efficiency in the all three blends mentioned above. This was attributed to the existence of long side chains, which improved the stability of the compatibilizers at the interface of immiscibe polymer blends.