MISCIBILITY BEHAVIOUR OF POLYMER BLENDS

Abstract

The miscibility behaviour of poly(dialkyl itaconates), poly(alkyl methacrylates) and polyketones was studied by differential scanning calorimetry (DSC). All the miscible blends were also examined for the lower critical solution temperature (LCST) behaviour. Specific intermolecular interactions in several blend systems were investigated by Fourier-transform infrared spectroscopy (FTIR) and solid state 13C nuclear magnetic resonance spectrometry ( 13C NMR). Four poly(dialkyl itaconates), namely, poly(dimethyl itaconate) (PDMI), poly(diethyl itaconate) (PDEI), poly(di-n-propyl itaconate) (PDnPI), poly(di-n-butyl itaconate) (PDnBI), and three poly(alkyl methacrylates), namely, poly(methoxy-carbonylmethyl methacrylate ) (PMOCMA), poly(glycidyl methacrylate) (POMA), poly(tetrahydropyranyl methacrylate) (PTHPMA), were studied in this work. Their miscibility with hydroxyl-containing polymers, chlorine-containing polymers and poly(styrene-co-acrylonitrile) (SAN) copolymer was investigated. The two polyketones studied in this work were poly(isopropenyl methyl ketone) (PIPMK) and poly(vinyl methyl ketone) (PVMK). PDMI and a low molecular weight PDEI sample were found to be miscible with poly(p-vinylphenol) (PVPh) over a molecular weight range of 1.7-30 kg/mol. FTIR studies show the existence of hydrogen-bonding interactions between the hydroxyl group in PVPh and the carbonyl group in poly(dialkyl itaconates). A molecular weight dependence on miscibility was observed for PDEI/PVPh blends. Only PDMI is miscible with poly(chloromethyl methacrylate) among all the chlorine-containing blends studied. In addition, ternary blends of PDMI/PDEI/poly(p-vinylphenol) (PVPh) show miscibility if the PVPh content is higher than 50 wt %. No miscibility window was observed for blends with SAN. The miscibility of poly(dialkyl itaconates) is very limited as compared with the corresponding poly(alkyl methacrylates). PMOCMA is partially miscible with PVPh. Unlike poly(acetonyl methacrylate) (PAcMA), PMOCMA is not miscible with SAN over the entire copolymer composition range. PGMA was found to be miscible with PVPh but PTHPMA was not. FTIR studies show the existence of intermolecular interactions between PMOCMA and PVPh but the interactions are not sufficiently strong to achieve complete miscibility. Similar to PVMK, PIPMK was found to be miscible with PVPh. However, both PVMK and PIPMK are immiscible with phenoxy. FTIR and solid state 13C NMR studies show the existence of hydrogen bonding interactions between PIPMK and PVPh. The present study reveals that although the presence of functional moieties in component polymers is important in achieving miscibility, an additional carbonyl group or ether oxygen atom does not necessarily lead to further improvement. Other effects, such as electronic effect and the structural factors of individual polymers may also affect the miscibility of polymer blends. The structural factors may include the length of pendant group, the ring size and the chain flexibility.