Effect of Amylose Derivatives on Thermal Properties of Poly(methyl methacrylate)
To investigate the effective procedure for controlled polymer structure and thermal properties through radical polymerization,amylose derivatives were used as chiral additives to induce the radical polymerization of methyl methacrylate(MMA).The effect of amylose derivatives on the structure and thermal properties of poly(methyl methacrylate)(PMMA)was subsequently explored.Four kinds of amylose derivatives were synthesized through carbamoylation,including amylose tri(4-chlorophenyl carbamate)(ACPC),amylose tri(phenylcarbamate)(ATPC),amylose tri(4-methylphenylcarbamate)(AMPC)and amylose tri(S-(-)-α-methylbenzyl carbamate)(ASMBC).The structures and degree of substitution of the amylose derivatives were characterized by magnetic resonance spectroscopy(1H-NMR)and circular dichroism(CD)spectra,demonstrating complete substitution and regular chiral helical structure of the obtained derivatives.The thermal stability of PMMA was assessed using differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA),revealing a significant enhancement in the thermal stability of PMMA induced by amylose derivatives.Furthermore,the substituents properties of the derivatives and the polarity of the polymerization solvent significantly influenced the radical polymerization behavior of MMA.Both bulk polymerization and solution polymerization were effective in improving the thermal properties of PMMA,with the solution polymerization system utilizing non-polar octane as the solvent achieving the most significant improvement.Among the amylose derivatives,the para-methyl-substituted amylose derivatives(AMPC)demonstrated the most effective induction effect,which could increase the glass transition temperature(Tg)and the onset decomposition temperature(To)of PMMA by 26 and 71 ℃,respectively.The induction mechanism of amylose derivatives was investigated using gel permeation chromatography(GPC),dynamic laser light scattering(DLS)and X-ray diffraction(XRD).The results indicated that MMA monomers could be arranged in order along the chiral helical cavity of the derivatives.This ordered arrangement can not only improve the structure order of polymer molecular chains,but also have a positive effect on its aggregation behavior,thereby achieving effective control of the thermal properties of PMMA.It suggests that the radical polymerization behavior and thermal properties of MMA can be effectively regulated by selecting appropriate helical polymers,offering a novel idea for exploring the controlled radical polymerization method of methacrylate monomers.
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