期刊
SOFT MATTER
卷 8, 期 15, 页码 4072-4082出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c2sm06915f
关键词
-
类别
资金
- Air Force Office for Scientific Research [FA9550-09-1-0169]
- National Science Foundation [EEC-0836633, DMR 09-69301]
- Foundation for Polish Science
- Ministry of Science and Higher Education [N508 3820 33]
- Directorate For Engineering
- Div Of Civil, Mechanical, & Manufact Inn [1234263] Funding Source: National Science Foundation
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [969301] Funding Source: National Science Foundation
The effect of polymer-graft modification on the structure formation and mechanical characteristics of inorganic (silica) nanoparticle solids is evaluated as a function of the degree of polymerization of surface-grafted chains. A transition from 'hard-sphere-like' to 'polymer-like' mechanical characteristics of particle solids is observed for increasing degree of polymerization of grafted chains. The elastic modulus of particle solids increases by about 200% and levels off at intermediate molecular weights of surface-grafted chains, a trend that is rationalized as a consequence of the elastic modulus being determined by dispersion interactions between the polymeric grafts. A pronounced increase (of about one order of magnitude) of the fracture toughness of particle solids is observed as the degree of polymerization of grafted chains exceeds a threshold value that is similar for both polystyrene and poly(methyl methacrylate) grafts. The increased resistance to fracture is interpreted as a consequence of the existence of entanglements between surface-grafted chains that give rise to energy dissipation during fracture through microscopic plastic deformation and craze formation. Within the experimental uncertainty the transition to polymer-like deformation characteristics is captured by a mean field scaling model that interprets the structure of the polymer shell of polymer-grafted particles as effective 'two-phase' systems consisting of a stretched inner region and a relaxed outer region. The model is applied to predict the minimum degree of polymerization needed to induce polymer-like mechanical characteristics and thus to establish 'design criteria' for the synthesis of polymer-modified particles that are capable of forming mechanically robust and formable particle solid structures.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据