Synthesis And Assembly Morphology Of Isotatic Polypropylene Miktoarm Star Copolymers

Isotactic polypropylene(i PP)is one of the largest material varieties in the field of polymer materials,and the total polypropylene production has increased year by year in the world.Due to the excellent mechanical properties and chemical stability,iPP can be widely used in industries and daily life.Multi-layer and multi-scale structural design in polymer molecular chains,crystal forms and phase states have been used to achieve high performance of polypropylene.Our work is devoted to the synthesis of a new isotactic polypropylene miktoarm star copolymer,and lays the foundation for exploring the performance and potential applications of such complex topological isotactic polypropylene.In this thesis,the synthesis of miktoarm star copolymers based on isotactic polypropylene was achieved by chemical methods such as coordination polymerization,reversible addition fragmentation chain transfer polymerization(RAFT)and coupling reaction.The main work and conclusions are as follows:(1)The propylene coordination polymerization was initiated by the metallocene compound rac-Et(Ind)2ZrCl2,and the iPP macromonomer with the silicon methoxy terminal group was synthesized by the styrene derivative TCSSt as the end-capping agent.TBDB were selected to initiate the RAFT polymerization,atactic polystyrene(aPS)macromonomers with adjustable molecular weight and the silicon methoxy terminal group were synthesized.The coupling reaction between silicon methoxy groups from iPP terminal and aPS terminal respectively was used to synthesize a series of iPP/aPS miktoarm star copolymers with 3-4 arms,adjustable arm length and adjustable composition.(2)The self-assembly behavior of iPP/a PS miktoarm star copolymers in N,N'-dimethylformamide(DMF)solution was studied.The results showed that the copolymer can form stable micelles in DMF,having the particle size between 200 and 1200 nm.The aggregate state of micelles after drying was presented in granular,and the particle shape is closely related to the copolymer composition.By adjusting the arm length and composition of the iPP/aPS miktoarm star copolymer,the particles can present different morphologies such as rods or spheres.By adjusting the morphology of the star copolymer particles,it is possible to obtain a superhydrophobic property(water contact angle ? 153o)and a self-cleaning function(water rolling angle ? 5o)polymer surface.(3)RAFT polymerization initiated by TBDB was carried out with N,N'-diethyl-2-acrylamide to synthesize poly(N,N'-diethyl-2-acrylamide)(PDEA)macromonomers with adjustable molecular weight and silicon methoxy terminal group.The coupling reaction between silicon methoxy groups from iPP terminal and PDEA terminal respectively was used to synthesize a series of iPP/PDEA miktoarm star copolymers with 5-8 arms,adjustable arm length and adjustable composition.(4)The self-assembly behavior of iPP/PDEA miktoarm star copolymers in ethanol solution was studied.The results showed that the copolymers could form stable micelles in ethanol,with size around 1200 nm.The aggregate state of micelles after drying can present irregular particle morphologies by adjusting arm length and composition of the iPP/PDEA miktoarm star copolymers.(5)Using the above synthesized macromonomers iPP,aPS and PDEA,three kinds of miktoarm star copolymers(iPP/aPS,iPP/PDEA,aPS/PDEA)which have similar arm lengths and arm numbers but different structures were prepared.And the particle morphologies of three kinds of miktoarm star copolymer micelles were compared.The results showed that the particle size of the copolymer iPP/aPS(~5 ?m)and iPP/PDEA(~1 ?m)is significantly larger than that of aPS/PDEA(~50 nm)due to the presence of iPP crystal phase,which indicates that the introduction of the crystalline polymer component in the copolymer micelles is advantageous for obtaining large-size particles.