Synthesis of Branched Polysiloxanes with Controlled Branching and Functionalization by Anionic Ring-Opening Polymerization

Abstract

Functionalized branched polysiloxanes with star-branched, comb-branched and dendritic-branched topologies were synthesized. The branched macromolecules were generated by coupling of reactive blocks using a grafting technique (ACS Polym. Prepr. 2001, 42, 227; ACS Symp. Ser. 2003, 838, Chapter 2). The living anionic ring-opening polymerization (ROP) of vinyl-substituted cyclotrisiloxanes (ViMeSiO)3, V3, and, VD2, and the copolymerization of these monomers with hexamethylcyclotrisiloxane, D3, was explored to obtain reactive blocks. Termination of the living polymer, having a lithium silanolate end group, on a reactive core containing SiCl groups led to the grafting of living polysiloxane on the core. Transformation of vinyl groups in the polymer into the reactive SiCl groups by hydrosilylation with Me2HSiCl made possible the grafting of a successive generation of branches. The reactive blocks of high and low density of the precursor vinyl group were obtained by the polymerization of monomers V3 and VD2, respectively. While the homopolymerization led to a uniform density of vinyl groups along the chain, the copolymerization of V3 or VD2 with D3 produced a gradient distribution with the density decreasing in the direction of the chain growth. This arrangement led to a higher density of the vinyl group in the external part of the branched macromolecule. Study of kinetics of the copolymerization of V3 with D3 in THF initiated by BuLi gave the reactivity coefficients k V 3 = 17.8, k D 3 = 0.036 (25 °C), from which the density distribution of vinyl groups in reactive blocks may be determined. Four-arm star copolymers were obtained using (MeCl2SiCH2)2 as the core, whereas the comblike polysiloxane was obtained from a linear copolymer of ViMeSiO and Me2SiO treated with Me2HSiCl. Dendritic polysiloxanes of the first and second generation were obtained using the functionalized starlike polysiloxane as the core.

Synthesis, formulation, and characterization of siloxane‐modified epoxy‐based anticorrosive paints

“…The gloss at 45°increased upon the incorporation of siloxane. The scratch hardness and impact resistance along with the bending test values increased markedly upon the incorporation of HP-DMS into E. This result was also in contrast to our expectations because siloxanes have unusual flexibility 7,8,13,22 on account of the flexible SiOO linkages and mobile silicone chains; they possess poor mechanical characteristics. 6 HPDMS was expected to behave as a flexibilizer.…”

“…14,15 These optimum characteristics have been obtained with the usage of inorganic siloxane polymers with acrylates, vinyls, acetoacetates, and epoxies. 9,10,14,15,19 -21 Siloxanes are known for unusual flexibility, 22 high thermal stability and moisture resistance, good dielectric properties, excellent UV and chemical resistance, 8,12,13,15,20,[23][24][25] low toxicity, 3,12 and high corrosion protective efficiency. 15 The conventional methods used to introduce siloxanes into polymers involve a common blending process.…”

Formation and Properties of Responsive Siloxane‐Based Polymeric Surfaces with Tunable Surface Reconstruction Kinetics

“…Implementing the thiol-ene addition reaction on PVMS networks, a route others demonstrated with fluid polymers, [15,[22][23][24] we modified PVMS substrates with 11-dodecanethiol (HS(CH 2 ) 11 CH 3 ) and 3-mercaptopropionic acid (HS(CH 2 ) 2 COOH). The addition to the vinyl bond was confirmed via the elimination of the C --C peaks at 960, 1407, and 1587 cm À1 in Fourier transform infrared spectroscopy in the attenuated total reflection mode (FTIR-ATR).…”

Development of Siliconized Epoxy Resins and Their Application as Anticorrosive Coatings

“…Silicone is suitable modifier for epoxy resins. The modified resin has superior thermal and thermo-oxidative stability, fracture energy, excellent moisture resistance, partial ionic nature, low surface energy and good hydrophobicity [9].…”