Study On The Segment-segment Interaction Parameters Of Fluorosilicone-containing Block Copolymers

The block copolymers containing fluorosilicone segments have good physical and chemical properties such as low surface energy,chemical inertness,heat resistance,weather ability and the like.As we know,one of the main features of block copolymers is the formation of microphase-separated structures as spherical(S),columnar(C),lamellar(L)and Gyroid(G)by thermodynamic interactions between segments.The main application of block copolymers is based on the unique physical properties given by the self-assembled phase behavior at this nanoscale.However,the microphase separation behavior of fluorosilicone-containing block copolymer is very special,and the effective value of the Flory-Huggins segment-segment interaction parameters between fluorosilicone and vinyl polymer segments is not clear.In this paper,the segment-segment interaction parameters of fluorosilicone-containing block copolymers were studied.In this work,a series of well-defined poly[methyl(3,3,3-tri-fluoropropyl)siloxane]-b-polystyrene(PMTFPS-b-PS)block copolymers and poly[methyl(3,3,3-trifluoropropyl)siloxane]-b-poly(methyl methacrylate)(PMTFPS-b-PMMA)block copolymers were obtained via atom transfer radical polymerization(ATRP).The effective values and their regularity of the segment-segment interaction parameters between the fluorosilicone block and PS or PMMA were investigated.The specific results of the study were depicted as follows:1.The PMTFPS-b-PS and PMTFPS-b-PMMA block copolymers were prepared by using PMTFPS-Br as the macro-initiator for ATRP reaction.(1)Through anionic ring-opening polymerization(AROP)with 1,3,5-trimethyl-1,3,5-trifluoropropyl cyclotrisiloxane(F3)as a monomer and terminated with dimethylchlorosilane,Si-H terminated PMTFPS(PMTFPS-H)was synthesized.With the hydrosilylation reaction of PMTFPS-H and allyl alcohol,followed the reaction with ?-bromoisobutylidene bromide,the product of PMTFPS-Br was obtained.(2)In the solvent of cyclohexanone,the ATRP reaction of MMA was carried out using CuBr/1,1,4,7,10,10-hexamethyltriethylenetetramine(HMTETA)as the catalyst system to obtain PMTFPS-b-PMMA block copolymer.The PMTFPS-b-PS block copolymer was also obtained by the reaction of ATRP in the presence of CuBr/(PMDETA)as the catalyst system.2.The microphase separation behavior of PMTFPS-b-PS and PMTFPS-b-PMMA block copolymers were investigated.(1)The results showed that there were two distinct glass transition temperatures(Tg)in the PMTFPS-b-PS and PMTFPS-b-PMMA block copolymers,which means there are microphase-separated microstructures in the block copolymers.This result was also confirmed by the transmission electron microscopy(TEM)experiments.Moreover,the Tg of the PMTFPS segment was-74 to-79? and the Tg of the PMTFPS segment was about 100-116?in the PMTFPS-b-PMMA block copolymer.The Tg of the PMTFPS segment in the PMTFPS-b-PS diblock copolymer was-70 to 73? and the Tg of the PS segment was about 86 to 104?.It was found that the microphase separation was possible if a small amount of fluorosilicone segments were contained in the block copolymers.(2)Order-disorder transitions(ODT)were found in the PMTFPS-b-PS and PMTFPS-b-PMMA block copolymers by the investigation with advanced rheological extension system(ARES),which also means there are microphase-separated microstructures in the block copolymers.3.The effective values of the segment-segment interaction parameters(?eff)between the PMTFPS block and PS or PMMA were investigated.(1)The change of the storage modulus G' of the block copolymers with the temperature was investigated by using ARES.The temperature of ODT or ODT critical point was determined by adjusting the length of the block chain(degree of polymerization,N),and different ODT critical points were obtained corresponding to the exact value of the transition temperature T and ?eff.And finally,the relationship between ?eff and temperature T was obtained as follows:PMTFPS-b-PS diblock copolymer: ?eff = 470/T-0.735PMTFPS-b-PMMA diblock copolymer: ?eff = 637/T-1.04(2)Under the same temperature,the segment-segment interaction parameters between the PMTFPS-b-PS and PMTFPS-b-PMMAS block copolymer segments were significantly larger than those of conventional block copolymers,because the chemical structure changed the intermolecular interactions,and then changed the effective value of the interaction parameters between the segments.