Study On The In-chain Functionalized Polymers Synthesized From 1,1-Diphenylethene Derivatives/Styrene

The living anionic polymerization (LAP) is one of the most typical living chain growth polymerization methods in polymer synthesis. Kinetics, thermodynamics and steric hindrance are the main methods to precisely control the sequence arrangement of functional polymers in the chain propagation of LAP. However, it needs to be further investigated how to influence the sequence arrangement in-chain of functional monomer units in functionalized polymers. Due to the distinct steric hindrance,1,1-diphenylethylene (DPE) and its derivatives cannot be homopolymerized via LAP. The functional groups of DPE derivatives can adjust the comonomers activity and reactivity ratio in LAP, and can regulate the sequence distribution in the corresponding copolymers. Additionally, different functional groups on phenyl rings of DPE derivatives could cooperate with each other and extend the application range of the corresponding in-chain functionalized polymers. However, there are few investigations into the synthesis of asymmetric multi-groups substituted DPE derivatives and the corresponding in-chain functionalized polymers. Moreover, the relationship between well-defined structure and properties of the in-chain functionalized polymers are also rarely reported. To resolve the above problems, this work was implemented and achieved the following results:1. Three types of asymmetric bi-functionalized DPE derivatives substituted by SiH groups (DPE-SiH/R) were successfully synthesized-DPE-SiH, DPE-SiH/OMe and DPE-SiH/NMe2. The corresponding polycarbosilane oligomers P(DPE-SiH/R) were obtaineded by the hydrosilylation polymerization of these DPE, and the molecular weights of P(DPE-SiH/R) are about 1.7?2.1 kgmol-1. Among the two types of isomer units in P(DPE-SiH/R), the ?-addition proportion of them was 85-88%. The reaction rate constants of DPE-SiH/OMe in the hydrosilylation polymerization is ?Khy=1.25×10-2 h-1 ([SiH]/[Pt]=1200,65 ?), and its apparent activation energy is Ea=-4.38 kJmol-1. The substituents in DPE phenyl rings could improve corresponding oligomer's thermal stability. TGA results showed that the decomposition temperature (Td5) of P(DPE-SiH), P(DPE-SiH/OMe) and P(DPE-SiH/NMe2) under nitrogen purging conditions are 270 ?,345 ? and 352 ?, respectively. Furthermore, the weight residues of both oligomers were approximately 20%when P(DPE-SiH) and P(DPE-SiH/OMe) were heated at near 1200 ? in nitrogen, suggested that they could be used as precursors to prepare SiC ceramic with hetero atoms.2. A series of in-chain functionalized copolymers, P(St-co-DPE-SiH/R), were prepared via LAP and initiated by sec-BuLi at 25 ? in benzene. The functionalized copolymers with different contents of styrene and functionalized DPE-SiH/R (DPE-SiH/OMe and DPE-SiH/NMe2) were investigated by varying the molar feed ratio ([Ms]0/[Md]0), and the corresponding average reactivity ratios, rS-O=1.42 and rs-N=1.79, were obtained. Furthermore, each sample was characterized by DSC, and the linear increasing relationships between the glass transition temperature of the copolymer (Tg) and the DPE derivatives weight percent in the copolymer (DPE derivative wt%) were obtained. The chain propagation process for the anionic copolymerization of styrene and DPE-SiH/R at [Ms]0[MD]o=4, were investigated by time sampling under high vacuum conditions, and the corresponding propagation rate constants were obtained. Furthermore, the statistical comonomer sequence arrangements in the corresponding copolymers were determinated simultaneously, and the copolymer of in-chain SiH pendant groups possessed gradient quadruple interval arrangement, P(St-9uad-DPE-SiH/OMe) and P(St-quad/-DPE-SiH/NMe2), were confirmed under the above conditions. At the same time, the alternating copolymer P(St-alt-DPE-SiH/OMe) and P(St-alt-DPE-SiH/NMe2) were obtained by adjusting the comonomer ratio in the polymer.3. The side grafted, multi-ketones and cross-linkable polymeric photoinitiators, PI-R/R', were synthesized by the hydrosilylation from ethynyl groups which substituted in the phenyl rings of monomolecular photoinitiators benzophenone derivatives (ER'BP), and SiH substituent groups of the in-chain functionalized copolymer, P(St-co-DPE-SiH/R), with determined topological structure and SiH pendant groups sequence arrangement. PI-R/R' included hereinafter well-defined structures:linear-shaped and side chains approximate quadruple interval arrangement (LQPI-R/R'), linear-shaped and side chains alternating arrangement (LAPI-O/R'), and 4-arms star-shaped and side chains alternating arrangement (SAPI-O/R'). Subsequently, PI-R/R'were used to initiate photopolymerization of 1,6-hexanediol diacrylate (HDDA) under UV light, and the results showed that the agminated side chains contained photoactive groups could strongly influence the induction period (tc10%) and the maximum reaction rate (RPmax) to the structural well-defined polymeric photoinitiators PI-O/R', and tc10% and tRPmax (the period of reaction rate reached the maximum) were sorted from short to longer:LQPI-O/R'<LAPI-O/R'<SAPI-O/R'. RPmax of LAPI-O/N was higher than LQPI-O/N and SAPI-O/N 43% in the case of system without coinitiators MDEA, and RPmax of LQPI-O/R'was higher than LAPI-O/R'and SAPI-O/N when MDEA added. The sterically hindered and conjugated double bonds in the side chains, which obtained in hydrosilylation, were crosslinked with active monomers during the photopolymerization. Accord to the test results from DMA, the crosslinking density of UV cured materials photoinitiated by PI-O/O were improved 49% than that photoinitiated by BP, the crosslinking density of UV cured materials photoinitiated by SAPI-O/O was higher than LAPI-O/O, and LQPI-O/O was higher than LAPI-O/O.