SYNTHESIS,STRUCTURE AND PROPERTIES OF COMB-LIKE COPOLYMER P(MMA-co-MAh)-g-PEGME

In order to improve the ionic conductivity of the poly(methyl methacrylate-co-maleic anhydride)(P(MMA-co-MAh))-based gel polymer electrolytes,the poly(ethylene glycol)methyl ether chains were introduced in the side of P(MMA-co-MAh)binary copolymer to prepare comb-like poly(methyl methacrylate-co-maleic anhydride)-g-poly((ethylene glycol)methyl ether)(P(MMA-co-MAh)-g-PEGME)copolymer.The comb-like copolymer P(MMA-co-MAh)-g-PEGME was synthesized through two esterification reactions.The esterification of P(MMA-co-MAh)with PEGME at first in butanone,then injecting a definite volume of p-toluenesulfonic acid into the reaction mixture under a flow of nitrogen.The mixture was stirred continuously for 24 h at 80℃.After the reaction was complete,solvent in the mixture was then removed.An excess amount of methyl alcohol and definite volume of dimethyl sulphate were added to the residue so as to thoroughly endcap the unreacted carboxyl groups.The reaction proceeded with continuous stirring for another 24 h at 60℃.The methyl alcohol in the reaction mixture was then removed.The crude product was purified by butanone/toluene reprecipitation,and dried at room temperature.Further more,the product must be purified three times using petroleum ether and de-ionized waters at 80℃ to get the purified product.The purified product was dried in a vacuum oven to remove the trapped solvent at 40℃ for 24 h.The final product is white power.The structure of the comb-like copolymer was characterized by Fourier transform infrared spectroscopy(FTIR),which showed that the characteristic absorption of CO in anhydride at 1851 cm-1 and 1786 cm-1 disappeared,and the absorption of a saturated cyclic five-member anhydride(OC—O—CO)also disappeared.While a strong characteristic absorption of an ether group at 1152 cm-1 is shown.This is an evidence that appreciable amount of the anhydride has been esterified and the product is an ester of poly(ethylene glycol)mono.The structure of P(MMA-co-MAh)-g-PEGME polymer was further examined by 13 C-NMR,1H-NMR and H,C-COSP spectra.The FTIR and NMR spectra indicated that the comb-like P(MMA-co-MAh)-g-PEGME copolymer was successful synthesized.The thermal properties of P(MMA-co-MAh)-g-PEGME were studied by thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The TGA indicated that the thermal stability of P(MMA-co-MAh)-g-PEGME polymer was littler lower than that of P(MMA-co-MAh)copolymer.The decomposition temperature of the comb-like polymer P(MMA-co-MAh)-g-PEGME is 325.9℃.The thermal stability of comb-like P(MMA-co-MAh)-g-PEGME copolymer and the P(MMA-co-MAh)copolymer are both better than that of the pure PMMA polymer.The DSC curves showed that the comb-like polymer P(MMA-co-MAh)-g-PEGME had two glass transition temperatures(T_g),the one glass transition of the main-chains,which was at around 120℃,and the other was about 32℃,which can be considered as the glass transition of the side-chains.The side-chains can move at room temperature,which will help to transfer and expand the electro active material.

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