Design And Synthesis Of α,ω-chain End Functionalized Polyolefins Based On Ylide Polyhomologation

Design and synthesis of α, ω-chain end functionalized polyolefins have become one of the hot research topic in recent years. The polyolefins not only can be used as polymer modifier, but also are starting points for other more complex structures, such as block copolymers, graft copolymers, and more complex polymer brushes. There are some methods for synthesizing α, ω-chain end functionalized polyolefins. In contrast to the traditional preparation method, the polyhomologation of ylides completes the construction of the molecular chain of polyolefin at one time by one carbon atom. By introducing trialkylborane in polyhomologation, reactive group terminated polyolefins can be obtained. Successive chemical modification of the chain end group can result in various polyolefins. In addition,it is also possible to prepare a wider variety of chain functional polyolefins in combination with click chemistry or to prepare block copolymers in combination with other polymerization processes.Firstly, in this work, we would like to report the synthesis of a series of well-defined a,ω-telechelic polymethylenes with hetero bi-/tri-functionalities based on the polyhomologation of ylides. A tandem strategy was employed, i.e., new organic boranes with one or two -CH=CH2 groups were prepared by the hydroboration of divinylbenzene or 1,3,5-triallyl-1,3, 5-triazine-2,4,6(1H,3H,5H)-trione (TAIC) using catecholborane and initiate in situ the polyhomologation of ylides. Subsequently, the post functionalization were carried out directly in the reaction system above-mentioned using end-capping reagents such as trimethylamine N-oxide dehydrate (TAO), I2 and tetraethylthiramdisulfide to achieve terminal -OH, -I and -SC(S)NEt2 respectively. The ’H NMR, 13C NMR, FT-IR, GPC and DSC were employed to characterize their structure, Mn and D. The terminal functionalities of 77-100% can be reached in different reaction system targeting various α, ω-telechelic polymethylenes. The molecular weights of the obtained polymers can be controlled in a broad range from 1260 to 13380 g/mol remaining narrow distribution (D= 1.04～1.12). The molecular weight of the three-arm polymethylene can be regulated by the ratio of ylide monomer and borane. And the functionalization rate was close to 100%.New chain end functionalized polymethylene can be obtained by thiol-ene "Click"reaction of TAIC-PM-OH with 3-mercapto-1, 2-propanediol and 2-(Boc-amino)ethanethiol in the presence of 2, 2-dimethoxy-2-phenylacetophenone which was used as photoinitiator.The polymer structure was confirmed by 1H NMR and FT-IR, and the chain functionalization rate was 100%.The block copolymers PM-b-PFSt and PM-b-P(St-co-FSt) were prepared by the thermal initiation and photoinitiation, respectively, using TAIC-PM-I and Mn2(CO)10. The structure,molecular weight and molecular weight distribution of the polymers were characterized by ~1H NMR, 19F NMR and GPC. Three-arm block copolymer was also obtained by thermal initiation, and characterized by ’H NMR and 19F NMR. Due to the excellent solubility of the three-arm copolymer, porous films were fabricated via static BF process in aqueous vapor atmosphere. The surface morphology and structure of the porous film were explored by scanning electron microscopy (SEM) and water contact angle. It was found that the ordered porous films could be prepared by using dichloromethane and chloroform as the solvent at 25℃. The porous films with good regularity were obtained in CH2Cl2 solution with polymer concentration of 5 mg/mL and average pore size of 1.06 μm. A highly ordered porous films with the pore size of 0.89 μm was formed at the concentration of 10 mg/mL with CHCl3 as solvent. The water contact angle increases with the regularity of the film, and the maximum water contact angle up to 124°, showing good hydrophobicity.