Synthesis of Cyclolinear Poly(carbosilane)-g-poly(methyl methacrylate or styrene) Random Copolymers

Abstract

The cyclolinear polycarbosilane, (poly(1-hexyl-1,3-ditolyl-1,3-disilacyclobutane) poly(HDTDSCB)), which has tolyl groups attached to the main chain Si atoms, was prepared by ADMET polymerization with the second-generation Grubbs catalyst, and 10%, 5%, and 2% of the tolyl groups were brominated by reactions with N-bromosuccinimide. A series of well-controlled poly(methyl methacrylate) (PMMA) anions of 2.5K, 5K, and 10K molecular weight were introduced via the "grafting onto" strategy at low temperature to the randomly 10%, 5%, and 2% brominated poly(HDTDSCB), respectively, without any lithiation or ring opening of the disilacyclobutane in the main chain. Because of side reactions initiated by the PS anion under similar conditions, a "grafting from" strategy by ATRP was employed to yield the corresponding poly(HDTDSCB)-g-PS random copolymers. The product poly(HDTDSCB)-g-(PMMA or PS) random copolymers were purified by using total adsorption-desorption interaction chromatography, which involves selective adsorption of the polycarbosilane on a C18 HPLC column from a CH 2 Cl 2 /CH 3 CN (50/50) eluent, while the excess PMMA or PS homopolymer eluted. This method was also successfully applied to the separation of larger quantities of the copolymers by using multiple injections onto the C18 column.

Cyclolinear polycarbosilanes – a recent addition to the class of organosilicon polymers

“…27 Nonetheless, the same ATRP graft-from approach (Scheme 6) was successfully applied to the tolyl-substituted cyclolinear polycarbosilane, [-{RSi(CH 2 ) 2 SiR}-(CH 2 ) 6 -] n poly-(hexyleneditolyldisilacyclobutane or HDTDSCB) (M n = 10 K; PDI = 1.9, Tg = -6 • C) to prepare a poly-(HDTDSCB)-g-PS graft copolymer, without appreciable ring-opening. 38 It was suggested that the absence of RO in this case could be due to the relatively low temperature for the ATRP reaction as compared to the initiation temperature for the CuBr-catalyzed DSCB RO and/or the stabilized nature of the radical site in ATRP, along with the low concentration of radical species.…”

“…In the latter approach, a macrocyclic anion was prepared separately by controlled anionic polymerization and added to the randomly brominated poly-(HDTDSCB) (Scheme 7). 37,38 Due to the relatively basic character of the polystyrene anion, some ring opening of the disilacyclobutane moieties in the main chain of poly-(HDTDSCB) was evidenced in efforts to apply this "graft onto" strategy with 6% brominated poly-(HDTDSCB), even at -78 • C in THF or in cyclohexane. 38 On the other hand, successful grafting without appreciable ring-opening was achieved with the PMMA anion in THF as long as the temperature was maintained at -78 • C. In order to maintain an approximately Scheme 6 Preparation of a PMTSM-g-PS copolymer by a graft-onto procedure.…”

Acyclic dienemetathesis: a versatile tool for the construction of defined polymer architectures

“…Soc. Rev., 2011, 40, 1404-1445 1435 the utility of ADMET for synthesising inorganic/organic hybrid polymers containing main group elements such as polycarbosilanes, 31,180,181,[184][185][186][187] poly(carbosiloxane)s, 188 polycarbogermanes, [189][190][191] polycarbostannanes, 190,192 polyferrocenes, 193,194 and transition metal-containing polymers. [195][196][197] Furthermore, organic polymers with pendant cyclophosphazene rings can be addressed as an example of the latter category of hybrid materials.…”

Inorganic and organometallic polymers

“…57 Polycarbosilane was grafted with poly(methyl methacrylate) (PMMA) or polystyrene (PS) to form random copolymers 23. 58 Molecular weights of the PMMA copolmers ranged from 17 000-19 000 g mol À1 (PDI = 2.1-5.0) whereas the styrene copolymers exhibited molecular weights from 13 000-20 000 g mol À1 (PDI = 2.2-2.6). Cationic, water soluble, conjugated polysilanes were prepared which exhibited blue-emission and were highly sensitive to quenching agents such as [Fe(CN) 6 ] 4making them attractive as sensors.…”