New polymers with tuneable dielectric properties were prepared by modifying trimethylsilyl end-terminated poly(methylhydro)siloxane with polar γ-cyanopropyl groups. The amount of polar groups was tuned by adjusting the allyl cyanide/n-hexene ratio in poly(methylhydro)siloxane co-hydrosilylation. The copolymers were characterized by FTIR and NMR spectroscopy. The distribution of the polar groups along the chain was evaluated based on ¹H NMR spectroscopy. The influence of the amount of polar γ-cyanopropyl on the glass transition temperature (T_g) and on the dielectric properties was investigated by DSC and impedance spectrometry. All polymers showed T_gs well below room temperature. A linear increase in permittivity (ε′) with increasing amount of γ-cyanopropyl groups was observed. A maximum ε′ value of 15.9 for the copolymer containing 89 mol% polar groups was achieved, which is 6-fold higher than polydimethylsiloxane. The incomplete conversion of Si–H groups observed in all hydrosilylation reactions with allyl cyanide opened up the possibility of using the prepared copolymers as cross-linkers.

A series of polar silicones was synthesized in order to compare their dielectric properties. Different substituents with high dipole moment (epoxy, pyridyl, aldehyde, cyano-, nitroazobenzene) were attached by hydrosilylation to a poly(dimethyl-methylhydro)siloxane. Thiol-ene addition on a dimethyl-methylvinyl siloxane copolymer with similar composition was also used for chemical modifications with chloro- or carboxy- derivatives. This approach allowed comparison of properties with emphasis on dielectric behavior measured in liquid state, as a preliminary step in design and preparation of materials suitable for dielectric elastomers. Although a relatively low content of polar groups was used (8%), permittivity values of 5.4 and even 7.4 were achieved (at 10 kHz), either due to the large dipole moment or to the presence of important amounts of moisture. The water sorption capacity of the polar silicones was investigated by dynamic vapor sorption, while structural parameters of model molecules were calculated, in order to correlate the dielectric properties with the polarity/hydrophilicity of the substituents to the silicone chain. A combined effect of the calculated dipole moment, molar polarizability, molar volume, and the measured water sorption capacity on dielectric permittivity was observed.

Elastic materials with increased permittivity (ε′) were obtained in a three-step process starting from a hydroxyl end-functionalized polydimethylsiloxane (PDMS) of a high molecular weight (M_w = 139 kDa), trimethylsilyl end-blocked silicones that carry hydrosilane, cyanopropyl and hexyl groups P_x (where x represents the mol% of cyanopropyl groups), and tetraethoxysilane (TEOS). The hydrosilane groups of P_x were first hydrolyzed and the formed hydroxyl groups were subsequently reacted with partially hydrolyzed TEOS and further used as high ε′ components, cross-linkers, and reinforcing agents for the PDMS matrix. A high wt% of the polar component P_x was incorporated into the nonpolar PDMS matrix by forming interconnected networks. Thermal (DSC, DMA) and morphological investigations (SEM) show the biphasic morphology of the networks. The dielectric, mechanical, and electromechanical properties of the films were investigated. Materials with good elastic properties, increased ε′, and a high breakdown field (E_b) were obtained. The best material has an elastic modulus of 800 kPa at 10% strain, an ε′ = 4.5, and a maximum actuation strain of 8% at E_b = 56 V μm⁻¹.

Mesoporous silica nanoparticles (MSNs) bearing methyl, thiol or glucose groups were synthesized, and their encapsulation and release behaviors for the anticancer drug Doxorubicin (Dox) were investigated in comparison with nonporous homologous materials. The chemical modification of thiol-functional silica with a double bond glucoside was completed for the first time, by green thiol-ene photoaddition. The MSNs were characterized in terms of structure (FT-IR, Raman), morphology (TEM), porosity (nitrogen sorption–desorption) and Zeta potential measurements. The physical interactions responsible for the Dox encapsulation were investigated by analytic methods and MD simulations, and were correlated with the high loading efficiency of MSNs with thiol and glucose groups. High release at pH 5 was observed in most cases, with thiol-MSN exhibiting 98.25% cumulative release in sustained profile. At pH 7.4, the glucose-MSN showed 75.4% cumulative release, while the methyl-MSN exhibited a sustained release trend. The in vitro cytotoxicity was evaluated on NDHF, MeWo and HeLa cell lines by CellTiter-Glo assay, revealing strong cytotoxic effects in all of the loaded silica at low equivalent Dox concentration and selectivity for cancer cells. Atypical applications of each MSN as intravaginal, topical or oral Dox administration route could be proposed.