Preparation And Characterization Of Alkylaminated Poly(styrene-co-maleic Anhydride) Comb Polymers

Comb-like polymer is a special kind of polymer,composed of two types of main chain and side chain.With its excellent physical and chemical properties,it has been widely used.With the continuous improvement of synthesis methods,different types of comb-like polymers began to emerge.Polystyrene-co-maleic anhydride(SMA)is a commercial polymer material with good chemical properties and low price.It has been widely used in various fields such as automobile internal structural parts,various electrical enclosures,and medical devices.However,the presence of active acid anhydride groups in SMA leads to unsatisfactory weather resistance and heat resistance and limits the application.In this paper,a series of alkyl aminated and alkylated comb-like polymers with different side chain lengths,denoted as SMACnN and SMICnN(n=12,14,16,18,number of carbon atoms in n-alkyl side chain),are successfully prepared by amidation(ring-opening reaction)and imidization(ring-closing reaction).The thermal behavior,side chain crystallization,conformational transition and phase transition of SMACnN and SMICnN are studied by variable temperature-Fourier transform infrared spectroscopy(VT-FTIR),liquid hydrogen nuclear magnetic resonance spectra(¹H NMR),differential scanning calorimeter(DSC),variable temperature wide-angle X-ray diffractometer(VT-WAXS),thermogravimetric analysis(TG)and gel chromatography(GPC).For the SMACnN comb-like polymer,The thermal behavior increases with the increase of alkyl side chain length,and the enthalpy value increases from 6.0 k J/mol(C₁₄NH₂)to 17.6 k J/mol(C₁₈NH₂).When the number of carbon atoms in the side chain is higher than 12,the crystallization behavior of SMACnN can be observed,which indicates the rigid main chain limitation of SMA.At low temperature,only?_Hphase(hexagonal phase)is formed in SMAC18N comb-like polymer,which is similar to that of rigid comb-like polymer alkylated polyaniline(PBA-Cn),which indicates that the rigid main chain has a great influence on the crystallization behavior of side chain.Similarly,the formation of conformational disorder is also supported by the low temperature and variable temperature infrared.The results of DSC,XRD and VT-FTIR showed that SMICnN comb-like polymer was amorphous and in a conformational disorder state,in which trans conformation and gauche conformation coexisted.After amidation,the thermal stability of SMA was significantly improved,which was higher than that of SMA.SMICnN comb-like polymer shows obvious hydrophobic characteristics.