Modulation Of Nanostructures In Thermosetting Polymers By Using Amphiphilic Copolymers

Recently, it has been realized that incorporating amphiphilic block copolymers into thermosetting polymers can obtain the nanostructured thermosets with improved mechanical and functional properties. A series of amphiphilic copolymers such as AB diblock, ABA triblock, hyperbranched block copolymer and grafted copolymers were synthesized via the combination of ring-open polymerization, reversible addition-fragmentation chain transfer polymerization(RAFT), atom transfer radical polymerization(ATRP) and click chemistry reaction. In this work, it was explored to use the these amphiphilic copolymers to control the formation of the nanostructures in several crosslinked polymers.The morphology and formation mechanisms of nanostructures in crosslinked polymers containing amphiphilic copolymers were characterized by means of small-angle X-ray scattering(SAXS), atomic force microscopy(AFM) and transmission electron microscopy(TEM). Furthermore, the properties of the nanostructured materials were investigated. The main results were summarized as follows:1. The poly(?-caprolactone)-b-poly(3-hexylthiophene)-b-poly(?-caprolactone)(PCL-b-P3HT-b-PCL) triblock copolymer was synthesized via ROP polymerization. The PCL-b-P3HT-b-PCL triblock copolymer was incorporated into epoxy to prepare the spherical and cylindrical nanostructured epoxy thermosets. It was found that the formation of the nanostructures was in a self-assemble manner in thermosets. With increasing the content of the triblock copolymer, the glass transition temperatures(Tg’s) of nanostructured epoxy thermosets decreased while the dielectric permittivity(ε) and the thermal conductivity increased at the room temperature.2. The four block copolymers containing polystyrene and poly(4-vinylpyridine) segments with the different topologies were synthesized via RAFT and ATRP polymerization. All of the block copolymers were incorporated into phenolic resin to obtain the worm and spherical nanostructured phenolic resins and porous carbon materials. It was found that nanostructures morphology of both phenolic resins and porous carbon materials could be modulated by changing the topologies of block copolymers with same molecular weight and composition.3. AB2-type hyperbranched poly((?-caprolactone)-b-(polystyrene)2) copolymer(h-P[PCL-b-(PS)2]) was synthesized via the combination of ROP,ATRP and copper-catalyzed Huisgen 1,3-dipolar cycloaddition. The h-P[PCL-b-(PS)2 was incorporated into epoxy resin to obtain the worm and spherical nanostructured thermosets. It was found that the formation of the nanostructures was in a reaction-induced microphase separation manner. The glass transition temperatures(Tg’s) of nanostructured thermosets decreased with increasing the content of the hyperbranched block copolymer.4. Grafted copolymer poly(norbornenyl poly(ethylene glycol)-r-norbornenyl polystyrene [P(NB-PS-r-NB-PEO)]was synthesized via the combination of RAFT and ROMP. In aqueous solutions, the amphiphilic P(NB-PS-r-NB-PEO) random copolymers were self-assembled into spherical micelle-like nanoobjects as evidenced by DLS and TEM. Furthermore, The P(NB-PS-r-NB-PEO) was incorporated into epoxy resin to obtain the worm and spherical nanostructured thermosets via following the mechanism of reaction-induced microphase separation. Grafted copolymer poly(vinylidene fluoride-co-trifluoroethylene)-g-polymethyl methacrylate[P(VDF-CTFE)-g-PMMA]was synthesized via atom transfer radical polymerization(ATRP).Then the P(VDF-CTFE)-g-PMMA was incorporated into epoxy resin to obtain spherical nanostructured thermosets. Compared with pure epoxy thermosets, the hydrophobic property and dielectric permittivity(ε) of nanostructured epoxy thermosets containing P(VDF-CTFE)-g-PMMA were dramatically strengthened.5. The poly(N-isopropylacrylamide)-b-poly(sodium p-styrene sulfonate)(PNIPAM-b-PSSNa)and poly(N-isopropylacrylamide)-g-poly(sodium p-styrene sulfonate)(PNIPAM-g-PSSNa)were sythesized via RAFT polymerization, respectively. The nanostructured PNIPAM-b-PSSNa and PNIPAM-g-PSSNa hydrogels were successfully obtained. It was found that the volume phase transition temperature and swelling ratio of the modified hydrogels increased with increasing the content of the PSSNa. In comparison with the control PNIPAM hydrogel, the deswelling and reswelling of the modified hydrogels was in accelerated fashions. The rapid thermoresponse of the modified hydrogels was attributable to the formation of PSSNa nanophases in PNIPAM networks.