Molecular Weight Dependence of Domain Structure in Silica-Siloxane Molecular Composites

1992 ◽  
Vol 274 ◽  
Author(s):  
Tamara A. Ulibarri ◽  
Greg Beaucage ◽  
Dale W. Schaefer ◽  
Bernard J. Olivier ◽  
Roger A. Assink
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Composite Materials ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Precursor Polymer ◽  
Molecular Weight Dependence ◽  
Molecular Composites ◽  
Filler Phase

ABSTRACTA detailed investigation of the molecular weight dependence of silica growth in in situ filled polydimethylsiloxane/tetraethylorthosilicate (PDMS/TEOS) materials was conducted using small angle neutron scattering (SANS). Composite materials were produced by using TEOS to simultaneously produce the glassy filler phase and to crosslink linear, hydroxyl terminated PDMS of variable molecular weight, M. Correlated domains of glassy filler were produced. The morphology of the in situ filled material showed a definite dependence on the molecular weight of the precursor polymer. The scale, R, of the glassy domains follows de Gennes' description of phase separation in a crosslinked system (R ∝ M1/2).

Polycarbodiimide and polyimide/cyanate thermoset in situ molecular composites

1998 ◽  
Vol 13 (7) ◽  
pp. 1840-1847 ◽  
Author(s):  
D. R. Wiff ◽  
G. M. Lenke ◽  
P. D. Fleming
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Phase Separation ◽  
Molecular Mechanics ◽  
High Molecular Weight ◽  
Molecular Composites ◽  
Rigid Rod ◽  
Composite Reinforcement

The synthesis of polycarbodiimide and polyimide in a cyanate resin precursor was achieved. A unique procedure for achieving a high molecular weight of the molecular composite reinforcement molecules was demonstrated. In spite of phase separation being present during the processing, the final cured composites were transparent. The enhanced mechanical properties and the presence of a single Tg, which increases with rigid rod content, were indications that a molecular composite was achieved. The agreement between measured mechanical properties and those predicted using molecular mechanics simulations CERIUS2 software was encouraging.

Structure of Microphase-Separated Silica/Siloxane Molecular Composites

1989 ◽  
Vol 171 ◽  
Author(s):  
Dale W. Schaefer ◽  
James E. Mark ◽  
David Mccarthy ◽  
Li Jian ◽  
C. -C. Sun ◽  
...  
Keyword(s):  
Phase Separation ◽  
Kinetic Studies ◽  
Organic Content ◽  
Small Particles ◽  
X Ray ◽  
Filled Elastomers ◽  
Polymeric Networks ◽  
Large Particles ◽  
Molecular Composites

ABSTRACTThe structure of several classes of silica/siloxane molecular composites is investigated using small-angle x-ray and neutron scattering. These filled elastomers can be prepared through different synthethic protocols leading to a range of fillers including particulates with both rough and smooth surfaces, particulates with dispersed interfaces, and polymeric networks. We also find examples of bicontinuous filler phases that we attribute to phase separation via spinodal decomposition. In-situ kinetic studies of particulate fillers show that the precipitate does not develop by conventional nucleation-and-growth. We see no evidence of growth by ripening whereby large particles grow by consumption of small particles. Rather, there appears to be a limiting size set by the elastomer network itself. Phase separation develops by continuous nucleation of particles and subsequent growth to the limiting size. We also briefly report studies of polymer-toughened glasses. In this case, we find no obvious correlation between organic content and structure.

Self-assembly behavior of ultra-high molecular weight in-situ anionically synthesized polymer matrix composite materials “grafted from” single- or multi-wall CNTs

Polymer ◽  
2021 ◽  
Vol 235 ◽  
pp. 124243
Author(s):  
Evangelos Kasapis ◽  
Konstantina Tsitoni ◽  
Gkreti-Maria Manesi ◽  
Ioannis Moutsios ◽  
Dimitrios Moschovas ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Composite Materials ◽  
High Molecular Weight ◽  
Matrix Composite ◽  
Polymer Matrix ◽  
Self Assembly ◽  
Polymer Matrix Composite ◽  
Assembly Behavior ◽  
Ultra High Molecular Weight

scholarly journals Phase separation in titanium hydrides studied by small-angle neutron scattering

1993 ◽  
Vol 03 (C8) ◽  
pp. C8-287-C8-290 ◽  
Author(s):  
I. O. BASHKIN ◽  
A. I. KOLESNIKOV ◽  
V. Yu. MALYSHEV ◽  
E. G. PONYATOVSKY ◽  
S. BORBÉLY ◽  
...  
Keyword(s):  
Phase Separation ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering

Large-Angle X-ray Scattering and Small-Angle Neutron Scattering Study on Phase Separation of Acetonitrile−Water Mixtures by Addition of NaCl

2001 ◽  
Vol 105 (26) ◽  
pp. 6236-6245 ◽  
Author(s):  
Toshiyuki Takamuku ◽  
Atsushi Yamaguchi ◽  
Daisuke Matsuo ◽  
Masaaki Tabata ◽  
Midori Kumamoto ◽  
...  
Keyword(s):  
Phase Separation ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Large Angle ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Neutron Scattering Study ◽  
Ray Scattering

scholarly journals Variation of Solvent Scattering-Length Density in Small-Angle Neutron Scattering as a Means of Determining Structure of Composite Materials

1994 ◽  
Vol 376 ◽  
Author(s):  
Rex P. Hjelm ◽  
Wesley Wampler ◽  
Michel Gerspacher
Keyword(s):  
Composite Materials ◽  
Carbon Black ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Scattering Length ◽  
Contrast Variation ◽  
Length Scales ◽  
Excluded Volume Effects ◽  
Component Form

ABSTRACTAs part of our work on the structure of composite materials we have been exploring the use of small-angle neutron scattering using the method of contrast variation to dissect the component form, structure and distribution. This approach has resulted in a new look at very old problemreinforcement of elastomers by carbon black.Using this approach we studied an experimental high surface area (HSA) carbon black and a gel of "HSA-bound" rubber in cyclohexane/deuterocyclohexane mixtures. HSA in cyclohexane is found to be short rodlike particle aggregates. The aggregates have a shell-core structure with a high density graphitic outer shell and an inner core of lower density amorphous carbon. The core is continuous throughout the carbon black aggregate, making the aggregate a stiff, integral unit. Contrast variation of swollen composite gels shows that there are two length scales in the gel structure. Above 10 Å, scattering from carbon black predominates, and below 10 Å the scattering is from both carbon black and the elastomer. The HSA in the composite is completely embedded in polyisoprene. An estimate of the carbon black structure factor shows strong exclusion of neighboring aggregates, probably from excluded volume effects. The surface structure of the carbon black is unaltered by the interactions with elastomer and appears smooth over length scales above about 10 Å. These results show that contrast variation can provide information on composite structure that is not available by other means. This information relates to the reinforcement mechanism of elastomers by carbon blacks.

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