Preparation Of Brush Polymers And Study On Their Self-assembly

Brush block copolymers are a type of block copolymers with high grafting-density and regular side-chain arrangement.The steric hindrance of the high grafting-density of side chains makes the backbone adopt an extension conformation,which lead to rapidly self-assemble into ordered structures.In this thesis,symmetric brush block copolymers were synthesized,and one-dimensional photonic crystal thin films were prepared by the self-assembly of the corresponding brush block copolymers.For this purpose,an initiator modified with norbornenyl group for atom transfer radical polymerization(ATRP)was synthesized,and three different molecular weight norbornene modified poly(tert-butyl acrylate)(NB-PtBA)macromonomers were synthesized via ATRP.Then a series of poly[norbornene-poly(tert-butyl acrylate)](P[NB-Pt BA])brush homopolymers were synthesized by ring-opening metathesis polymerization(ROMP)to investigate the effect of side chain length and the main chain length on the ceiling degree of polymerization(CDP)for P[NB-PtBA] brush polymers.Kinetic studies on ROMP of NB-PtBA showed that there was a CDP for the brush polymer,for macromonomer with molecular weight of 2-3k,the CDPs were estimated to be approximately 400,and for 8k,the value was approximately 100.Based on the study of CDP,norbornene-polystyrene(NB-PS)with a molecular weight of 3.2k and norbornene-poly(tert-butyl acrylate)(NB-PtBA)macromonomer with a molecular weight of 3.6k were synthesized.And then a series of symmetric brush block copolymers P[NB-PS]-b-P[NB-PtBA] were synthesized by sequential ROMP of the NB-PS and NB-PtBA macromonomers.Then one-dimensional photonic crystal thin films were prepared by self-assembly of P[NB-PS]-b-P[NB-PtBA] brush block copolymers via controlled evaporation of the solvent.The main reflection wavelength increased linearly with increasing of molecular weight,and the main reflection wavelength could be reached to 480 nm.In addition,the thermal self-assembly of one-dimensional photonic crystal thin films was conducted using P[NB-PS]-b-P[NB-PtBA] to investigate the effect of temperature on the domain spacing of photonic crystal materials.Thermoresponsive one dimensional photonic crystals were obtained,which extended the applications of photonic crystals.