Telechelic siloxanes with hydrogen‐bonded polymerizable end groups. I. Liquid rubbers and elastomers

Abstract

Functional siloxanes are widely used in the synthesis of model networks used in rubber elasticity studies, and various functional siloxanes are also used in the synthesis of silicone rubbers. We present here the results of studies of two classes of telechelic, free-radically polymerizable siloxanes carrying either amide or urea groups attached at both ends of siloxane chain. The presence of polar, hydrogen-bonding end-groups favors the formation of aggregates which is reflected in the drastically increased viscosity of the resulting ''liquid rubbers.'' In addition, such aggregation accounts for high local concentrations of reactive groups thus making it possible to have high molecular weight precursors undergo facile room temperature polymerization. In this article, we study the effect of the nature of these functional groups on the viscosity of polymerizable ''liquid rubbers,'' finding that the different endgroups lead to dramatically different viscosities. We also study the silicone rubber films obtained by a UV-initiated free-radical polymerization of the liquid rubbers, using dynamic mechanical analysis and large-strain uniaxial deformation. We find here that important properties such as plateau modulus and Young's modulus are highly dependent on both endgroup type and precursor molecular weight. The crosslinking of telechelic siloxanes in dilution was also studied to further explore the effect of crosslink density of the mechanical properties of the model networks. Finally, we evaluated the role of dangling ends within the networks through the incorporation of monofunctional macromers.

Silicone containing copolymers: Synthesis, properties and applications

“…PDMS-amide networks were prepared by the UV initiated free radical polymerization of telechelic acrylamido and methacrylamido terminated PDMS oligomers with <M n > values of 5000 to 55,000 g/mol (194,195). Due to the extremely flexible PDMS matrix and substantial differences in the solubility parameters of PDMS and amide groups, which are15.5, and 43.2 (J/cm 3 ) 1/2 respectively (179), these crosslinked polyamides showed microphase separation and formed fairly strong films due to the strong hydrogen bonding between the amide hard segments.…”

α‐Thiophene end‐capped styrene copolymer containing fullerene pendant moieties: Synthesis, characterization, and gas sensing properties

“…Polymers can be functionalized at both side chain and chain end to improve their properties for different applications. Fullerene (C 60 ) is one of the most popular examples to be functionalized .…”

Nghiên cứu khả năng bảo vệ chống ăn mòn của màng sơn polyuretan biến tính với trietoxyphenyl silan

“…[1] Trong đó, các polyme kết hợp với nhau bởi liên kết Van der Waals hoặc liên kết hydro. [2] Phương pháp phổ biến nhất được sử dụng trong quá trình blend hóa giữa polysiloxan và polyuretan hoặc với các loại polyme khác đó là phương pháp khuấy trộn, với mục đích làm giảm sức căng bề mặt của polysiloxan trong blend, tăng độ bám dính giữa hai pha và tăng độ ổn định. Các chất hoạt động bề mặt được được sử dụng rộng rãi cho quá trình chế tạo blend.…”

“…Màng được chế tạo bằng phương pháp tạo màng ly tâm trên máy Filmfuge 1110N (Sheen) với tốc độ 600 vòng/phút. Chiều dày màng sau khi khô khoảng 30 m. Phản ứng xảy ra theo phương trình (2).…”