Reflectivity of Soft X-Rays by Polymer Mixtures

1988 ◽  
Vol 143 ◽  
Author(s):  
T. P. Russell ◽  
W. Jark ◽  
G. Comelli ◽  
J. Stöhr
Keyword(s):  
Phase Separation ◽  
Vinylidene Fluoride ◽  
Surface Films ◽  
X Rays ◽  
Polymer Mixtures ◽  
Energy Component ◽  
Annealing Conditions ◽  
Surface Behavior ◽  
Poly Vinylidene Fluoride ◽  
Profile Characteristic

AbstractThe specular reflectivty of soft x-rays has been used to investigate the surface behavior of mixtures of poly(vinylidene fluoride), PVF2, and poly(methyl methacrylate), PMMA. Mixtures where the concentration of PMMA is 0.8 where investigated as a function of the preparation and annealing conditions. It was found that mixtures prepared by rapidly casting from dimethylformamide, DMF, exhibited a gradient in the concentration of the two components. The gradient extended over large distances and was such that PMMA, the higher surface energy component was located preferentially at the surface. With annealing at 165°C, the width of the gradient diminished but the concentration of PMMA remained high at the surface. Films of the mixtures prepared under a slower solvent evaporation procedure produced a reflectivity profile characteristic of a phase separated mixture. The extent of phase separation was reduced with annealing. In all cases the roughness of the surface of the films was found to be 5.OÅ or less.

Simulations of High-Strain Electrostrictive Chlorinated Terpolymers

2003 ◽  
Vol 785 ◽  
Author(s):  
George J. Kavarnos ◽  
Thomas Ramotowski
Keyword(s):  
Vinylidene Fluoride ◽  
High Strain ◽  
Polymer Chains ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lamellar Structures ◽  
Annealing Conditions ◽  
Poly Vinylidene Fluoride ◽  
Electromechanical Responses ◽  
Kinetics Of

ABSTRACTChlorinated poly(vinylidene fluoride/trifluoroethylene) terpolymers are remarkable examples of high strain electrostrictive materials. These polymers are synthesized by copolymerizing vinylidene fluoride and trifluoroethylene with small levels of a third chlorinated monomer. The electromechanical responses of these materials are believed to originate from the chlorine atom, which, by its presence in the polymer chains and by virtue of its large van der Waals radius, destroys the long-range crystalline polar macro-domains and transforms the polymer from a normal to a high-strain relaxor ferroelectric. To exploit the strain properties of the terpolymer, it is desirable to understand the structural implications resulting from the presence of the chlorinated monomer. To this end, computations have been performed on model superlattices of terpolymers using quantum-mechanical based force fields. The focus has been on determining the energetics and kinetics of crystallization of the various polymorphs that have been identified by x-ray diffraction and fourier transform infrared spectroscopy. The chlorinated monomer is shown to act as a defect that can be incorporated into the lamellar structures of annealed terpolymer without a high cost in energy. The degree of incorporation of the chlorinated monomer into the crystal lattice is controlled by annealing conditions and ultimately determines the ferroelectric behavior of the terpolymers.

Does dynamic vulcanization induce phase separation?

Soft Matter ◽  
2014 ◽  
Vol 10 (30) ◽  
pp. 5550-5558 ◽  
Author(s):  
Mohammad Mahdi Abolhasani ◽  
Fatemeh Zarejousheghani ◽  
Minoo Naebe ◽  
Qipeng Guo
Keyword(s):  
Phase Separation ◽  
Crosslink Density ◽  
Vinylidene Fluoride ◽  
Dynamic Vulcanization ◽  
Miscible Blends ◽  
Poly Vinylidene Fluoride ◽  
Induce Phase Separation ◽  
Induce Phase

Immiscible and miscible blends of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) were subjected to dynamic vulcanization to investigate the effect of crosslink density on phase separation.

scholarly journals A Review on Porous Polymeric Membrane Preparation. Part I: Production Techniques with Polysulfone and Poly (Vinylidene Fluoride)

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1160 ◽  
Author(s):  
XueMei Tan ◽  
Denis Rodrigue
Keyword(s):  
Phase Separation ◽  
Vinylidene Fluoride ◽  
Solvent System ◽  
Processing Parameters ◽  
Membrane Preparation ◽  
Polymeric Membrane ◽  
Ambient Conditions ◽  
Membrane Fabrication ◽  
Core Technology ◽  
Poly Vinylidene Fluoride

Porous polymeric membranes have emerged as the core technology in the field of separation. But some challenges remain for several methods used for membrane fabrication, suggesting the need for a critical review of the literature. We present here an overview on porous polymeric membrane preparation and characterization for two commonly used polymers: polysulfone and poly (vinylidene fluoride). Five different methods for membrane fabrication are introduced: non-solvent induced phase separation, vapor-induced phase separation, electrospinning, track etching and sintering. The key factors of each method are discussed, including the solvent and non-solvent system type and composition, the polymer solution composition and concentration, the processing parameters, and the ambient conditions. To evaluate these methods, a brief description on membrane characterization is given related to morphology and performance. One objective of this review is to present the basics for selecting an appropriate method and membrane fabrication systems with appropriate processing conditions to produce membranes with the desired morphology, performance and stability, as well as to select the best methods to determine these properties.

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