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Do Very Small POSS Nanoparticles Perturb s-PMMA Chain Conformations?
Macromolecules ( IF 5.5 ) Pub Date : 2018-07-11 00:00:00 , DOI: 10.1021/acs.macromol.8b00432
Nicolas Jouault 1 , Sanat K. Kumar 2 , Robert J. Smalley 3 , Changzai Chi 3 , Robert Moneta 3 , Barbara Wood 3 , Holly Salerno 3 , Yuri B. Melnichenko 4 , Lilin He 4 , William E. Guise 3, 5 , Boualem Hammouda 6 , Michael K. Crawford 3, 7
Affiliation  

Small-angle neutron scattering (SANS) measurements of syndiotactic s-PMMA polymers mixed with weakly attractive 1.0 nm diameter polyhedral oligomeric silsesquioxane (POSS) nanoparticles (NPs) show no observable changes in the chain radius of gyration Rg, regardless of the polymer molecular weights, the amount of residual solvent, or the POSS NP loading and dispersion (from 0 to 20 vol %). In retrospect, these results are not surprising since scaling arguments imply that chain size in the concentrated region of the phase diagram of a polymer solution is ideal and independent of the polymer volume fraction ϕ, and only as the semidilute region is entered with decreasing concentration does the chain size for a good solvent begin to increase due to polymer excluded volume and then scales with concentration as ϕ–1/8. For typical polymer nanocomposites the NP concentrations are less than 50% v/v, so the polymers are still generally within the concentrated regions of their phase diagrams, where ideal chain conformations are observed for small molecule solvents. By combining the present results with previous results from the literature, we conclude that spherical NPs apparently have little effect on the conformations of polymer chains, especially in typical polymer nanocomposites that only incorporate moderate amounts of NPs.

中文翻译:

很小的POSS纳米颗粒会干扰s-PMMA链构象吗?

间规的s-PMMA聚合物与弱吸收性1.0 nm直径的多面体低聚倍半硅氧烷(POSS)纳米颗粒(NPs)混合的小角中子散射(SANS)测量显示回转链R g的链径没有可观察到的变化,无论聚合物分子量,残留溶剂的量或POSS NP的负载量和分散度(0至20 vol%)如何。回想起来,这些结果并不令人惊讶,因为比例论据暗示聚合物溶液相图中浓缩区的链长是理想的,并且与聚合物体积分数independent无关,并且只有随着浓度降低而进入半稀释区时,由于聚合物排除体积,良好溶剂的链大小开始增加,然后随着浓度成concentration –1/8发生缩放。对于典型的聚合物纳米复合材料,NP浓度小于50%v / v,因此聚合物通常仍处于其相图的集中区域内,在该区域内可观察到小分子溶剂的理想链构象。通过将当前结果与文献的先前结果相结合,我们得出结论,球形NP显然对聚合物链的构象影响很小,特别是在仅掺入适量NP的典型聚合物纳米复合物中。
更新日期:2018-07-11
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