Nanostructured Thermosets Containing Block Copolymers And Carbon Nanotubes:Preparation,Morphologies And Properties

In this dissertation,several block copolymers were synthesized via reversible additionfragmentation chain transfer(RAFT)polymerization,atom transfer radical polymerization(ATRP)and ring opening polymerization(ROP)approaches.These block copolymers were incorporated into epoxy to obtain nanostructured thermosets.In the meantime,multi-walled carbon nanotubes(MWCNTs)were also functionalized with polymer chains via RAFT and ring opening polymerization approaches.These block copolymers and polymer-grafted MWCNTs were employed to obtain the nanostructured thermosets.The correlations of structure with properties were investigated.The main contents of this dissertation are listed as below:1.Poly(ethylene oxide)-block-poly(((4-vinylphenyl)ethene-1,1,2-triyl)triben zene)(PEO-b-PTPEE)block copolymer was synthesized via RAFT polymerization approach.The block copolymer was incorporated into epoxy to invesgiate reactioninduced fluorescence enhancement behavior.Before curing reaction,mixtures of epoxy precursors with diblock copolymer only emitted feeble fluorescence under UV irradiation.However,the photoluminescence was significantly enhanced after curing reaction.This novel FL enhancement phenomenon resulted from aggregation-induced emission behavior of PTPEE blocks,which was triggered by curing reaction.In addition,the epoxy thermosets displayed enhanced dielectric constants due to the promoted contribution from electron polarizations via ?-? conjugation in the materials.2.Poly(ethylene oxide)-block-poly(6-(4-(4-cyanophenylazo)phenoxy)hexyl methacrylate)(PEO-b-PCPHM)block copolymer was synthesized via ATRP approach.This block copolymer was incorporated into epoxy to investigate the effect of trans-cis photoisomerization of azobenzene on the nanostructures of epoxy thermosets.To control the configuration of azobenzene moieties of PCPHM block,the curing reactions were carried out in the absence and/or presence of UV irradiation,respectively.Without UV irradiation,PCPHM microdomains were generated with trans configuration of azobenzene.Under UV irradiation,however,PCPHM microdomains were formed with cis configuration of azobenzene moieties.The trans and cis configurations of azobenzene moieties were significantly fixed with the occurrence of curing reactions.The nanostructured thermosets with trans azobenzene moieties can emit fluorescence,which is in sharp contrast to those with cis azobenzene moieties.In addition,the sizes of PCPHM microdomains with cis configuration of azobenzene moieties were significantly larger than those with trans configuration.The difference in configuration of azobenzene moieties also led to the difference in thermal and dielectric properties of the materials.3.Multi-walled carbon nanotubes(CNTs)were functionalized with poly(?-caprolactone)(PCL)via a surface grafting polymerization approach.The PCL-grafted CNTs were incorporated into epoxy to obtain the nanocomposites.It was found that the CNTs were homogenously dispersed into epoxy matrix with good integrity.The introduction of CNTs endowed the nanocomposites with enhanced dielectric constants and thermal conductivities.4.Multi-walled carbon nanotubes(CNTs)were functionalized with poly(acryloyl carbonate)(PA6CC),a polymer bearing 6-membered cyclic carbonate groups via a surface RAFT polymerization approach.It was found that the PA6 CCgrafted CNTs were readily dispersed in the mixtures of 6-membered bicyclic carbonate and tris(2-aminoethyl)amine.By initiating curing reaction,polyhydroxyurethane(PHU)nanocomposites were successfully obtained.CNTs were well dispersed in the continuous PHU matrix with good integrity.The PHU nanocomposites displayed improved thermal properties,mechanical properties,thermal conductivities,dielectric constants and shape memory properties.In addition,the nanocomposites preserved the reprocessing properties at elevated temperature.The reprocessing properties bestowed the shape memory materials with the reprograming ability of original shapes.