Synthesis And Properties Of Novel Functional Polyolefin Tri-block Copolymer

The design and synthesis of block copolymers incorporating polyolefins segments and other more polar segments could broaden the scope of application of polyolefins greatly and it has become one of hot topics in the functionalization of polyolefin in recent years. In addition, among the countless stimuli-responsive polymer, temperature-responsive polymer is the most interesting intelligence material for its broad application prospects in many areas. In this thesis, two kinds of well-defined temperature-responsive triblock copolymers based on polymethylene were synthesized via the combination of living polymerization of ylides and reversible addition-fragmentation chain transfer polymerization(RAFT). The molecular structure and weight of all the polymerization products were characterized. Furthermore, the properties of the both triblock copolymers in self-assembly, preparation of microporous polymer films and polymer blends were investigated. The content of this study can be divided into the following sections:1. Well-controlled functional polyolefins block copolymers PM-b-PNIPAM and PM-b-PNIPAM-b-PS were obtained by RAFT polymerization. Firstly, hydroxyl terminated polymethylene(PM-OH, Mn=1100, Mw/Mn=1.09) was prepared via polyhomologation of ylides. Then the macromolecular chain transfer agent(PM-CTA) was obtained via an esterification of smallmolecular chain transfer agent(CTA) with PM-OH. A series of PM-b-PNIPAM diblock copolymers were obtained by RAFT polymerization of NIPAM using PM-CTA as chain transfer agent. Subsequently, PM-b-PNIPAM-b-PS triblock copolymers were prepared via RAFT polymerization of styrene. The 1H-NMR, FT-IR and GPC were employed to determine the chain structures, molecular weight and molecular weight distributions of all the polymerization products.2. A series of functional polyolefins PM-b-PS and PM-b-PS-b-PNIPAM copolymers were prepared by RAFT polymerization as above and their chain structures were characterized by 1H-NMR, FT-IR and GPC.3. The self-assembly behavior of the both functional polyolefins triblock copolymers was studied. The micellar forms were observed by transmission electron microscopy(TEM) and the average diameters of micelles were measured by dynamic light scattering instrument(DLS). The microporous films of such triblock copolymers were fabricated via breathe-figure method in water or methanol atmosphere and the film morphology was investigated via SEM. Furthermore, the cross-linked filmes under UV irradiation were also detected. Additionally, the LDPE/PS blends were prepared using PM-b-PNIPAM-b-PS as compatibilizer and the cryo-fractured surface of such blend polymers were observed by SEM.