Chemical modification of poly(n-hexylsilane) - Synthesis of functional polysilanes bearing thienyl groups on the appended sila-alkyl side chains and their application in the generation and stabilization of silver nanoparticles

The linear polysilanes [{RR′₂Si(CH₂)_ySi(n-hex)}_x{HSi(n-hex)}_1−x]_n (1-4; R = 2-thienyl, R′ = H; R = Me, R′ = 2-thienyl; y = 2, 3) have been synthesized by hydrosilylation reaction between preformed poly(n-hexylsilane) and (2-thienyl)vinyldichlorosilane/allyl(2-thienyl)dichlorosilane/bis(2-thienyl)methylvinylsilane/allyl-bis(2-thienyl)methylsilane using AIBN as the free radical initiator. GPC analysis reveals a monomodal molecular weight distribution in each case with M_w = 2492-3280 and PDI = 1.18-1.44. The polysilane 1 (R = 2-thienyl, R′ = H, y = 2) acts as reducing agent towards silver tetrafluoroborate under mild conditions (cyclohexane, rt, 5 h) to afford spherical silver nanoparticles of size 8.4 ± 0.7 nm, as evident from the TEM and dynamic light scattering (DLS) studies. The silver nanoparticles in the polymer matrix exhibit surface plasmon absorption at 420 nm suggesting the donor-acceptor interaction between the thienyl group and the metal nanocluster surface. This stabilization effect provides long shelf life stability to the nanoparticles in solution with no sign of agglomeration even after three months.