Synthesis Of Functional Polyolefins And Copolymers By Ring-Opening Metathesis Polymerization

As the traditional plastic commercial products,polyolefins have been developed rapidly in the past decades.However,due to their non-polarity,there are still problems existing,such as weak adhesion,toughness,miscibility,rheology,etc.Therefore,it’s necessary to improve these defects by introducing polar functional groups.Based on its living polymerization character,ring-opening metathesis polymerization(ROMP),has been developed fast in the recent years.Besides,the advantages,such as mild reaction conditions and environment friendly,also make it an excellent method to synthesize the functional polyolefins.This thesis aimed at synthesizing the side-chain functional polyolefins.The ROMP of cyclooctene derivatives was used as the main synthesis method to synthesize ethylene/vinyl ester copolymers with pendent linear branches and homopolymers and copolymers bearing bromo propionic acid ester groups.Furthermore in combination with the thiol-bromo "click" reaction,the side-chain functionalized polyolefins and crosslinking polymers were prepared.The major achievements of this thesis are as follows:(1)The four fatty acid derived cyclooctenes bearing different side chain length were prepared via epoxidation,reduction and esterification reactions from 1,5-cyclooctadiene.The side-chain functionalized polymers bearing different side chains were synthesized by ring-opening metathesis polymerization of these four monomers using Grubbs 2nd generation catalyst.The saturated polymers were achieved through chemical hydrogenation with TSH/TPA reagents,which could be regarded as the equivalents of a series of ethylene/vinyl ester copolymers with pendent linear branches on precisely every eighth backbone carbon.It was found that the molecular weight of unsaturated polymers increased with the increase in the concentration of monomers and the PDI ranged from 1.69 to 2.10.The DSC results indicated that the Tg of the polymers with shorter brancheswas below-55 ℃,whereas no significant Tg was observed for the polymers with longer linear branches.TGA analysis showed that the hydrogenated polymers had relatively better thermal degradation stability than the unsaturated polymers.(2)The reaction between 5-hydroxyl-cyclooctene and 2-bromopropiomyl bromide generated the monomer,cyclooctene bearing bromo propionic acid ester group at the 5-position.The ROMP of this monomer and copolymerization with cyclooctene with Grubbs 2nd generation catalyst produced the unsaturated polymers and copolymers with side chains of bromo propionic acid ester groups.The further chemical hydrogenation with TSH/TPA afforded the corresponding saturated polymers.It was found that the random copolymers had narrow PDI(1.68-1.78)and both homopolymers and copolymers had the similar GPC curves.The DSC results showed that the crystallization temperature(melting temperature)of the random copolymers decreased with the increase in the content of functional monomer in the copolymers and the Tg of the hydrogenated homopolymer was 40 ℃ higher than the corresponding unsaturated homopolymer.The functionalized polyolefins with the side chains of hydroxyl and carboxyl groups were successfully prepared through the thiol-bromo "click" reaction between the hydrogenated polymers and thiol compound.