Acyclic diene metathesis (ADMET) polymerization. Design and synthesis of unsaturated poly(carbosiloxanes)

Abstract

The synthesis of unsaturated poly(carbosiloxane)s, a new class of siloxane polymers possessing a perfectly alternating siloxane and alkenylene main chain, is presented. 1,5-Bis(allyl)-1,1,3,3,5,5hexamethyltrisiloxane (4), l,3-bis(4-pentenyl)tetramethyldisiloxane (6), 1,1,3,, and telechelic a,a)-di-4-pentenylpoly(l,l,3,3-tetramethyldisiloxanylpentylene) (10) undergo acyclic diene metathesis (ADMET) polymerization catalyzed by [(CF.ihCHsCOLUV-^.e-CeH.ri-Pr2)Mo=CHC(CH:i)2Ph (1). These polymerizations, which are performed under bulk conditions and at low temperatures, continuously release ethylene to give poly(l,l,3,3,5,5-hexamethyltrisiloxanyl-2-butenylene) (5), poly(1,1,3,3-tetramethyldisiloxanyl-4-octenylene) (7), poly(1,1,3,3-tetramethyldisiloxanyl-p-phenylenel,l,3,3-tetramethyldisiloxanyl-2-butenylene) (9), and poly(l,1,3,3-tetramethyldisiloxanylpentylene-co-l,1,3,3tetramethyldisiloxanyl-4-octenylene) (11), respectively. Bis(vinyl)tetramethyldisiloxane fails to homopolymerize under ADMET conditions, and bis(allyl)tetramethyldisiloxane (2) releases ethylene when catalyzed by 1 in the absence of solvent, to give, exclusively, the ring-closed product, 1,1,3,3-tetramethyldisiloxacyclohept-5-ene (3). Extending the methylene units or the siloxane linkage in the monomer results in facile ADMET polycondensation, in essentially quantitative conversions, affording well-defined, low-Tg, linear polymers with known vinylic end groups. The polymerizations are void of competing reactions except when back-biting reactions are favorable. Polymer 5 undergoes back-biting to generate the nine-membered cyclic silaoxalkene 13, when active polymer is diluted or, to a lesser extent, when in the bulk. All monomers and polymers were characterized by infrared spectroscopy and , 13C, and 29Si NMR spectroscopy. Number average molecular weights were determined by gel permeation chromatography and quantitative 13C NMR end group analysis when possible. Synthesis, characterization, thermal analysis, and the current scope of this polymerization are discussed.

Poly(p-phenylene alkylene)s – A forgotten class of polymers

“…With the latter, perfectly linear 1,4-polybutadiene 141) , as well as polymers [142][143][144] and copolymers 145,146) of 1,5-hexadiene and 1,9-decadiene with number-average molecular weights, M -n , up to 57 000 142) were synthesized. In addition to the relatively high molecular weights and the readily available monomers, ADMET polymerization proved to be a viable synthetic route to polymers, possessing various functionalities such as ethers 147) , thioethers 148) , silanes 149) , siloxanes 150) , esters 151) , ketones 152) , carbonates 153) , amines 154) , boronates 155) , stannanes 156) , and alcohols 157) . A synthetic route for poly(p-phenylene alkylene)s employing this methodology is, thus, suggested in Scheme 3 f.…”

Reactions of dilithiobutadienes with monochlorosilanes: Observation of facile loss of organic groups from silicon

“…Silanes 10a [22], 10b [23], and 10c [24], and siloxanes 11a [25] and 11b [26] were prepared as follows, and purified by [26]. 1,3,4, [16,27] was prepared from 0.3380 g (0.81 mmol) of diiodide 1 in 4 mL of anhydrous ether cooled to À64°C, and 0.65 mL (1.63 mmol) of n-BuLi (2.5 M in hexanes) (then warmed to 10°C over 45 min, and then cooled to À64°C) followed by 0.20 mL ($0.82 mmol of chlorosilane) of a mixture of equal volumes of Me 2 SiCl 2 and Et 3 N in 4 mL of THF (dropwise).…”

Selective photo-crosslinking of microphase-separated multiblock copolymers of poly(dimethylsiloxane) and phenylene diacrylate polyesters

“…The acid chloride of para-phenylenediacrylic acid was prepared using thionylchloride and then reacted with 4-pentene-1-ol, yielding para-phenylenediacrylic acid dipent-4-enyl ester (1) in 78% yield. Monomer 1 was employed in an acyclic diene metathesis (ADMET) polymerization [39,40], catalyzed by a ruthenium catalyst (RuCl 2 (2CHPh) (PCy 3 ) 2 ) [41,42]. The molecular weight of the oligomer or polymer (2) obtained strongly depends on the reaction conditions.…”