Thermal performance and phase transformation of S-alkylated poly(vinyl chloride) comb-like polymers

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A series of S-alkylated poly(vinyl chloride) (PVCS(n)) comb-like polymers, where the S atom acted as the chemical junction between PVC backbone and alkyl side chain, were prepared through the nucleophilic substitution reaction between PVC and n-alkyl mercaptan. Structure and properties of PVCS(n) are analyzed by 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis and X-ray scattering. An ordered crystal structure for PVCS(n) comb-like polymers appears with the increased side-chain length, which is originated from the regular packed side-chain crystallites. The increased carbon atoms per side chain from n = 12 to 18 also brings an improved thermal property. Obviously regular packed orthorhombic (βO) phase easily appears at room temperature, indicating the flexible PE backbone can allow much more CH2 groups entering an ordered phase structure. Phase transformation from βO to hexagonal phase is demonstrated by the temperature-dependent FTIR and WAXS. The chain packing manner for the pended side alkyl chains onto PVC backbone shows a dependence upon side-chain length, and the chemical junction also presents a certain influence on the phase transformation of side-chain crystallites. The variations for the phase behavior, chain packing and thermal property of PVCS(n) are detailed analyzed and characterized from the aspect of side-chain crystallization.