Synthesis, structural and adhesive evaluation of novel graft meth(acrylate) copolymers

A facile and inexpensive method of enhancing the adhesion of poly(methyl methacrylate) (PMMA) to the polyolefins polyethylene (PE) and polypropylene (PP), two commercially important but incompatible polymer classes, using a layer of graft copolymer has been demonstrated. In the present work a series of copolymers containing polyethylene, docosyl or branched alkyl grafts along a poly(methyl acrylate) or poly(methyl methacrylate) trunk were synthesised, characterised and adhesion tested. The graft copolymers were prepared by means of free radical polymerisation and grafting through procedure using macromonomers. Characterisation of the copolymers was achieved by NMR spectroscopy and SEC analysis where possible. The vinyl macromonomers employed in the polymerisation reactions were prepared by a straightforward esterification of commercially available starting materials. The copolymers were also tested using both an in-house and a standard method to determine their effectiveness as an adhesive in lap joints. When annealed above their melting temperature thin films of copolymers from the prepared series were found to provide strong adhesion between plaques of polyolefin and PMMA. The effects of overall molecular weight, mole ratio of (meth)acrylate backbone to PE side-chain and side-chain length and branching on adhesive performance were also investigated. Interestingly graft copolymers with a rather low PE content (~10-20%) proved to provide the best adhesion. In addition a method of purifying and characterising the commercially available polyethylene mono-alcohol by column chromatography was found. The mechanism of adhesion was probed using SEM, TEM and EDX spectroscopy of a cryo-fractured adhesion test piece and further investigation of the adhesive-PMMA interface was carried out using ULAM-ToF SIMS. The morphology of a series of PMA-g-PE copolymers of different compositions was investigated using TEM. Graft copolymers with low PE content (i.e. the best adhesives) showed no evidence of microphase separation whereas copolymers with higher PE content displayed evidence of continuous crystalline PE domains. Overall the PE grafts seem to increase compatability and toughness possibly acting as thermally labile crosslinks within the amorphous PMA matrix.A facile and inexpensive method of enhancing the adhesion of poly(methyl methacrylate) (PMMA) to the polyolefins polyethylene (PE) and polypropylene (PP), two commercially important but incompatible polymer classes, using a layer of graft copolymer has been demonstrated. In the present work a series of copolymers containing polyethylene, docosyl or branched alkyl grafts along a poly(methyl acrylate) or poly(methyl methacrylate) trunk were synthesised, characterised and adhesion tested. The graft copolymers were prepared by means of free radical polymerisation and grafting through procedure using macromonomers. Characterisation of the copolymers was achieved by NMR spectroscopy and SEC analysis where possible. The vinyl macromonomers employed in the polymerisation reactions were prepared by a straightforward esterification of commercially available starting materials. The copolymers were also tested using both an in-house and a standard method to determine their effectiveness as an adhesive in lap joints. When annealed above their melting temperature thin films of copolymers from the prepared series were found to provide strong adhesion between plaques of polyolefin and PMMA. The effects of overall molecular weight, mole ratio of (meth)acrylate backbone to PE side-chain and side-chain length and branching on adhesive performance were also investigated. Interestingly graft copolymers with a rather low PE content (~10-20%) proved to provide the best adhesion. In addition a method of purifying and characterising the commercially available polyethylene mono-alcohol by column chromatography was found. The mechanism of adhesion was probed using SEM, TEM and EDX spectroscopy of a cryo-fractured adhesion test piece and further investigation of the adhesive-PMMA interface was carried out using ULAM-ToF SIMS. The morphology of a series of PMA-g-PE copolymers of different compositions was investigated using TEM. Graft copolymers with low PE content (i.e. the best adhesives) showed no evidence of microphase separation whereas copolymers with higher PE content displayed evidence of continuous crystalline PE domains. Overall the PE grafts seem to increase compatability and toughness possibly acting as thermally labile crosslinks within the amorphous PMA matrix