Conformation of Arborescent Polymers in Solution by Small-Angle Neutron Scattering: Segment Density and Core-Shell Morphology

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• 作者：Seok Il Yun ; Kai-Chi Lai ; Robert M. Briber ; Steven J. Teertstra ; Mario Gauthier ; Barry J. Bauer
• 刊名：Macromolecules
• 出版年：2008
• 出版时间：January 8, 2008
• 年：2008
• 卷：41
• 期：1
• 页码：175 - 183
• 全文大小：265K
• 年卷期：v.41,no.1(January 8, 2008)
• ISSN：1520-5835

文摘

The radius of gyration (R_g) was determined as a function of generation number for arborescentpolystyrenes with two different side chain mass average molecular mass (M_w 5000, 5K, versus 30 000, 30K)by small-angle neutron scattering (SANS) measurements. The R_g values obtained were analyzed in terms of theZimm-Stockmayer model for randomly branched polymers, the scaling relation R_g M_w^v, and the expansionfactor _s = (R_g)_goodsolvent/(R_g)_solvent. The R_g and scaling exponent v = 0.26 ± 0.01 found for G0 through G3polymers with 5K side chains in cyclohexane-d correspond to the values predicted by the Zimm-Stockmayermodel. The R_g for G0 through G3 polymers with 30K side chains deviate from the model with v = 0.32 ± 0.02,corresponding to v = 0.33 expected for hard spheres. Deuterated polystyrene (PS-d) side chains were graftedonto G2 and G3 polystyrene (PS) cores. These copolymers, G2PS-graft-PS-d and G3PS-graft-PS-d, werecharacterized as spheres with a well-defined PS core-PS-d shell structure by the SANS contrast matching method.The shape and the segment radial density profile of the core and shell for GPS-graft-PS-d were determined basedon P(r) and (r) obtained by indirect Fourier transformation and deconvolution methods (P(r), pair distancedistribution function and (r) = (r) - (solvent), scattering length density contrast profile).