Spontaneous Nanoparticle Dispersal in Polybutadiene by Brush-Forming End-Functional Polymers
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- 作者：James M. Hart ; Solomon M. Kimani ; Lian R. Hutchings ; Isabelle Grillo ; Arwel V. Hughes ; Nigel Clarke ; Victoria Garcia-Sakai ; Sarah E. Rogers ; Budhika Mendis ; Richard L. Thompson
- 刊名：Macromolecules
- 出版年：2016
- 出版时间：February 23, 2016
- 年：2016
- 卷：49
- 期：4
- 页码：1434-1443
- 全文大小：565K
- ISSN：1520-5835
文摘
A masterbatch additive for the enhanced dispersal of bare silica nanoparticles in polybutadiene is demonstrated using tetrahydroxyl end-functional polybutadienes (“4OH-PBd”). Neutron reflectometry and small-angle neutron scattering (SANS) confirm the efficient end-adsorption of 4OH-PBd at a planar silica interface and silica particle interfaces of increasing complexity. SANS on well-defined model Stöber silica nanospheres in polybutadiene revealed spontaneous 4OH-PBd adsorption, forming a “shell” around the silica nanospheres. Analysis using a core–shell fractal model showed that the extent of adsorption was consistent with the interfacial excess determined by NR. The utility of 4OH-PBd additives to disperse silica nanoparticles was explored rigorously for a range of compositions and additives. Successful silica nanoparticles dispersal was evident from a reduction in the correlation length of the largest structures in the mixture and increase in fractal dimension, ascribed to a breakdown of percolating nanoparticle aggregates to smaller, denser clusters. A critical surface concentration of 4OH-PBd is identified, which is necessary to inhibit particle–particle aggregation. Scaling theory analysis over four different molecular weights of 4OH-PBd and several concentrations indicates that the transition in silica dispersal coincides closely to the transition from “mushroom” to “brush” scaling of the adsorbed 4OH-PBd. Rheological testing on the same composites yielded a dramatic decrease in moduli with increasing 4OH-PBd: silica ratio, particularly at low frequencies, which is consistent with the breakdown of large aggregates evidenced by SANS. Additives of this type could significantly simplify the processing of nanocomposites by eliminating the need for prior functionalization of the nanoparticles.