Construction of lamellar morphology by side-chain crystalline comb-like polymers for gas barrier

A comb-like polymer containing crystallized alkyl side chains and the intermolecular hydrogen bonds between the linking groups was fabricated by grafting long-chain fatty amine onto poly(styrene-co-acrylic acid)(n) (P(S-AA)(n), wherein "n" denoted AA feed ratio). The chemical structures and crystallization behaviors of the comb-like polymer P(S-AA)(n)-g(p) (wherein "p" denoted the number of side-chain carbon atoms) were analyzed by Fourier transform infrared, gel permeation chromatography, X-ray photoelectron spectroscopy, and X-ray diffractometer, differential scanning calorimetry, atomic force microscopy, respectively. It was found that the lamellar morphology could be generated by controlling the grafting density and side chain length of P(S-AA)(n)-g(p). Moreover, it was identified that the hydrogen bonds between amide groups could enhance the crystallinity and then adjust the interlamellar spacing of lamellar phase. As a result, P(S-AA)(70)-g(18) with the highest degree of crystallinity and closely packed lamellar morphology showed a good gas-barrier performance, and the nitrogen permeability reached 1.78 x 10(-14) cm(3)center dot cm/cm(2)center dot s center dot Pa. Furthermore, the permeation switch of the obtained comb-like polymer could reach 500 times traversing the melting point.