Synthesis,film morphology and performance of novel crosslinked polysiloxane with end-capped epoxy groups on cotton substrates

An epoxy group-terminated polyvinylmethylsiloxane (EPVMS) was firstly prepared via the cohydrolysis/condensation reaction of octamethylcyclotetrasiloxane (D₄), 2,4,6,8-Tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D₄V), and epoxy group-terminated polydimethylsiloxane (ETP) under a base catalyst. Then, the EPVMS was reacted with polymethylhydrosiloxane oligomer (PHMS) by hydrosilylation to develop novel crosslinked polysiloxane with end-capped epoxy groups (CLPS). The chemical structure and the thermal property of the as-prepared products were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectra (¹H/¹³C NMR) and thermogravimetric analysis (TGA). Finally, the CLPS was applied as the finishing agent to treat the cotton fabrics. The film morphology and the surface properties were examined with scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), contact angle measurements, and other instruments. FT-IR and NMR results confirmed the structure of the resultants. The crosslinked polysiloxane CLPS showed better thermal stability than the uncrosslinked polysiloxane EPVMS. The CLPS film on cotton fabric surface seemed to be smooth compared to the control by SEM. However, owing to the crosslinked structure, the CLPS film on silicon-wafer was inhomogeneous and had a few weak or strong peaks. At 5 nm data scale and in 2×2 μm² scanning field, the root mean square roughness of CLPS film reached to 0.414 nm. XPS analysis further demonstrates that there was a CLPS film covered on the cotton surface. Hydrophobicity of the CLPS treated fabric was superior to that of the EPVMS treated one. Whiteness of the treated fabrics by CLPS and EPVMS did not change at all compared to the control. The softness of the two treated fabrics was both better than that of control and particularly the softness of the EPVMS treated fabrics was preferable. The CLPS treated fabric possessed good washing durability.     

Copolymerization of benzyl methacrylate and a methacrylate bearing benzophenoxy and hydroxyl side groups: Monomer reactivity ratios,thermal studies and dielectric measurements

Statistical copolymers of 2-hydroxy-3-benzophenoxy propyl methacrylate (HBPPMA) and benzyl methacrylate (BzMA) in different feed ratios were synthesized by free radical copolymerization method at 60 °C in presence of AIBN initiator. The compositions of copolymer were estimated from ¹H-NMR technique. The monomer reactivity ratios of HBPPMA and BzMA were calculated as r₁ (r_HBPPMA)=0.51±0.076 and r₂ (r_BzMA)=1.07±0.140 for Kelen-Tüdos method, and was estimated as r₁=0.37±0.0006 and r₂=0.64±0.0485 according to Fineman Ross equation. The average values estimated from the two methods showed that monomer reactivity ratio of benzyl methacrylate was a slightly high in comparison to HBPPMA. The copolymer system showed an azeotropic point, which is equal to M _BzMA =m _BzMA =0.43. DSC measurements showed that the T_g’s of poly(HBPPMA) and poly(BzMA) were 84 °C and 73 °C, respectively. The T_g in the copolymer system decreased with increase in benzyl methacrylate content. The decomposition temperature of poly(BzMA) and poly(HBPPMA) occurs in a single stage at about 207 °C and 260 °C, respectively. Those of HBPPMA-BzMA copolymer systems are between decomposition temperatures of two homopolymers. The dielectric constant, dielectric loss factor and electrical conductivity were investigated depend on the frequency of the copolymers. The highest dielectric constants depending on all the studied frequencies were recorded for the poly(HBPPMA) and the copolymer containing the highest HBPPMA unit. The dielectric constant for P(HBPPMA) and P(BzMA) at 1 kHz are 6.56 and 3.22, respectively. Also, those of copolymer systems were estimated between these two values. Similarly, poly(HBPPMA) and copolymers, which are prepared under the same conditions show the dissipation factor and conductivity as well.