Tunable cohesion and water lubrication of PEG- g-PMHS- c-PMVS copolymer membranes

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2012-02, Vol.395, p.199-206
• Main Authors: Ding, Yan, Jiao, Zhan-Shi, Guo, Dong-Jie, Xiao, Shou-Jun, Tan, Wei, Dai, Zhen-Dong
• Format: Article
• Language: English
• Subjects: Cohesion; colloids; composite polymers; contact angle; Copolymers; energy; ethylene glycol; friction; Grafts; Hydrophilicity; Hydrosilylation; Lubrication; Poly (ethylene glycol); Polydimethylsiloxane; Silicone resins; spectroscopy; Surface energy; Water lubrication
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2011.12.031

A series of PEG-g-PMHS-c-PMVS elastomers were synthesized through two-step hydrosilylation reactions characterized by tunable cohesion and water lubrication properties. [Display omitted] ► A series of PEG- g-PMHS- c-PMVS elastomers with varying PEG concentrations are synthesized. ► Flexibility of the resultant copolymers increase with PEG concentration. ► Water lubrication performances of the copolymers gradually increase with PEG ratio. This paper reports a new technique that grafts poly (ethylene glycol) (PEG) onto polydimethylsiloxane (PDMS) to enhance the cohesion and water lubrication performances of PDMS. The technique employs a two-step hydrosilylation, using vinyl PEG, poly(methylhydrosiloxane) (PMHS), and poly(methylvinylsiloxane) (PMVS). Characterization of the hydrosilylation process was performed with attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy. Results showed that around 88% of active Si H function groups in PMHS were consumed to graft vinyl PEG and the rest were used to crosslink PMVS. Measurements of contact angles were used to determine the hydrophilicity and surface energy of the resultant PEG- g-PMHS- c-PMVS copolymers with varying PEG ratio. Results showed that both hydrophilicity and surface energy of the copolymers increased with the PEG ratio. Mechanical and cohesive characterizations of the copolymers showed that the flexibility of the copolymers increased with the PEG ratio, and thus normal preloads required to produce maximal cohesion forces or cohesion strengths decreased with increasing ratio of PEG. Results from friction tests further demonstrated that water lubrication performances of copolymers gradually increased with the PEG ratio. Our results suggested that the two-step hydrosilylation technique enhanced the formation of homogeneous mixtures between polar PEG and non-polar PDMS macromolecules. PMHS groups, through mediating PEG grafting onto PMVS, played an important role in improving PDMS properties, including hydrophilicity, flexibility, cohesion and water lubrication performances.