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Morphological implications of phase ...

Akki, Rashi.

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Morphological implications of phase transitions in polymer solutions: Inferences from polyacrylonitrile-based solutions.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Morphological implications of phase transitions in polymer solutions: Inferences from polyacrylonitrile-based solutions./
Author:	Akki, Rashi.
Description:	206 p.
Notes:	Source: Dissertation Abstracts International, Volume: 56-07, Section: B, page: 3781.
Contained By:	Dissertation Abstracts International56-07B.
Subject:	Chemistry, Polymer. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9537020

Morphological implications of phase transitions in polymer solutions: Inferences from polyacrylonitrile-based solutions.
Akki, Rashi.

Morphological implications of phase transitions in polymer solutions: Inferences from polyacrylonitrile-based solutions. - 206 p.

Source: Dissertation Abstracts International, Volume: 56-07, Section: B, page: 3781.

Thesis (Ph.D.)--Georgia Institute of Technology, 1995.

Solution-based processing of infusible polymers usually involves large quantities of undesirable solvents and transport-limited morphological evolution that is often difficult to control. The present study constitutes a rational exploration of the phase transitions in polymer solutions to form the basis for new processes that would diminish the above-mentioned problems and also identify appropriate mechanisms for controlled generation of useful morphologies. The fundamental concepts in this regard are exemplified through solutions of acrylonitrile-based homopolymer and copolymers, with important inferences drawn regarding their potential implications for the formation of fibers, films and membranes. Thermodynamic and kinetic manipulation of transitions such as liquid-liquid phase separation and crystallization is shown to be effective in controlled generation of morphologies ranging from microporous to dense.Subjects--Topical Terms:

1018428
Chemistry, Polymer.

Morphological implications of phase transitions in polymer solutions: Inferences from polyacrylonitrile-based solutions.
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035 $a (UnM)AAI9537020
035 $a AAI9537020
040 $a UnM $c UnM
100 1 $a Akki, Rashi. $3 1943168
245 1 0 $a Morphological implications of phase transitions in polymer solutions: Inferences from polyacrylonitrile-based solutions.
300 $a 206 p.
500 $a Source: Dissertation Abstracts International, Volume: 56-07, Section: B, page: 3781.
500 $a Adviser: A. S. Abhiraman.
502 $a Thesis (Ph.D.)--Georgia Institute of Technology, 1995.
520 $a Solution-based processing of infusible polymers usually involves large quantities of undesirable solvents and transport-limited morphological evolution that is often difficult to control. The present study constitutes a rational exploration of the phase transitions in polymer solutions to form the basis for new processes that would diminish the above-mentioned problems and also identify appropriate mechanisms for controlled generation of useful morphologies. The fundamental concepts in this regard are exemplified through solutions of acrylonitrile-based homopolymer and copolymers, with important inferences drawn regarding their potential implications for the formation of fibers, films and membranes. Thermodynamic and kinetic manipulation of transitions such as liquid-liquid phase separation and crystallization is shown to be effective in controlled generation of morphologies ranging from microporous to dense.
520 $a A framework has been developed here to relate the sequence of phase transitions that can occur when a polymer solution is cooled from a homogeneous state at a relatively high temperature to the resulting morphology in the crystallized polymer. Four distinctly different morphologies result from crystallization, (i) directly from a homogeneous solution (dense), (ii) following binodal LLPS with nucleation of the polymer-rich phase (GMP - globular microporous), (iii) following spinodal LLPS (FMP - fibrillar microporous), or (iv) following binodal LLPS with nucleation of the solvent-rich phase (CTMP - cell-tunnel microporous). The morphological sequence that arises from increasing the overall polymer concentration in such solutions has been shown to be dense $\ to\ \rm GMP \to\ FMP\ \to\ CTMP \to $ dense. The framework also serves to identify conditions (narrow temperature/concentration regions in the phase diagram) that can increase the likelihood of forming mixed or co-existing phases and the consequent morphologies.
520 $a Thermodynamic models to predict phase transitions in solution have to account for any strong association that might exist amongst the components. The study reported here comprised of certain simple modifications of current thermodynamic formulations for binary solutions, such as UNIFAC and Flory-Huggins lattice model. An association in two components was incorporated in UNIFAC (UNIFAC-A) and computations of UNIFAC and UNIFAC-A were compared both for solutions of small molecules and for polymers in low molecular weight solvents. Predictions considering association (UNIFAC-A) were much closer to the experimental data for liquid-liquid phase separation (LLPS) than the predictions of UNIFAC (without association). Flory-Huggins formulation was also modified to account for association between polymer segments and solvent molecules. However, quantitative implications of this "Associative Lattice Model" have not yet been explored.
590 $a School code: 0078.
650 4 $a Chemistry, Polymer. $3 1018428
650 4 $a Engineering, Chemical. $3 1018531
650 4 $a Textile Technology. $3 1020710
690 $a 0495
690 $a 0542
690 $a 0994
710 2 0 $a Georgia Institute of Technology. $3 696730
773 0 $t Dissertation Abstracts International $g 56-07B.
790 1 0 $a Abhiraman, A. S., $e advisor
790 $a 0078
791 $a Ph.D.
792 $a 1995
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9537020