Polysiloxane-Based Liquid Crystalline Polymers and Elastomers Prepared by Thiol–Ene Chemistry

Abstract

A series of side-chain liquid crystalline polymers (LCPs) with polysiloxane backbones have been synthesized by grafting mesogenic monomers to poly[3-mercaptopropylmethylsiloxane] (PMMS) via thiol–ene click chemistry. Their properties were studied in detail by a combination of 1H NMR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, polarized optical microscopy and small-angle X-ray scattering. In comparison with the traditional hydrosilylation method which requires noble metal catalyst platinum, this newly designed thiol–ene protocol produces polysiloxane-based LCPs with only anti-Markovnikov addition products under benign conditions. Moreover, by controlling the molar ratio of PMMS and mesogenic monomers, PMMS-based LCPs can be partially functionalized, meanwhile leaving spare mercapto groups, which could be further used as cross-linking sites to prepare polysiloxane-based liquid crystalline elastomers (LCEs). Besides preparing LCE fibers with a maximum contraction of 42% at nematic-to-isotropic transition temperature, we further explored the feasibility of using surface-rubbed cells to synthesize LCE films, but it turned out that this method could uniaxially align the mesogens of preformed short polymers but not the backbone chains so that the thermal-actuation effects of these films were modest.

Easily Processable and Programmable Responsive Semi‐Interpenetrating Liquid Crystalline Polymer Network Coatings with Changing Reflectivities and Surface Topographies

“…When macroscopically aligned, such materials also exhibit large dimensional changes, making them interesting as actuating polymers. Both stimulus‐responsive free standing films as well as LCEs confined to a solid substrate have been reported with programmable shapes and topographies . For CLC elastomers, dimensional changes along the helical pitch direction even resulted in changes in reflective color .…”

Highly Selective Hydrothiolation of Unsaturated Organosilicon Compounds Catalyzed by Scandium(III) Triflate

“…Sulfur‐containing organosilicon compounds are highly important as reagents and building blocks in complex organic structures such as polymers and dendrimers 6–8. These compounds are also well known in biology, medicine, and nanotechnology 9–11. Sulfur‐containing organosilicon systems have been used as photoplastic materials,12 in the treatment of retinal detachment,13 as superhydrophobic materials,14 in lithography15 and in the functionalization of paramagnetic materials 16…”

Polysiloxanes Modified by Thiol‐Ene Reaction and Their Interaction with Gold Nanoparticles

“…The thiol‐ene reaction has been increasingly used in the last years for functionalizing polysiloxanes . It has been used notably for preparing hydrophilic or amphiphilic polysiloxanes, surface functionalized PDMS elastomers, antibacterial silicones, elastomers for modulating cell adhesion, self‐healing polysiloxanes, polysiloxane elastomers with optical properties, liquid crystal polysiloxanes, electroactive ferrocene‐grafted polysiloxanes, polysiloxanes with tunable dielectric properties, or contact lens elastomers . Thiol‐ene strategy is also used in the case of polysiloxanes for getting an efficient, orthogonal cross‐linking, often initiated photochemically and consequently, has been adapted to electrospinning and 3D printing …”