Microporous membrane formation via thermally induced phase separation. I. Solid-liquid phase separation

Under a variety of circumstances commonly encountered in practice linear macromolecules crystallize into the form of thin platelets whose large upper and lower surfaces consist of an array of molecular folds. We refer to these as “chain-folded crystals” or “chain-folded lamellae,” the latter term usually being reserved for folded structures in polymers crystallized from the melt. The theory of the rate of formation of these platelets will be outlined, and the prediction and origin of the thin dimension given. The thin dimension of the crystal platelets is determined by kinetic factors, and the elucidation of the kinetics of growth is therefore of importance in polymer morphology on both a molecular and a macroscopic scale.

The Rate of Crystallization of Linear Polymers with Chain Folding

Crystallization, structure and properties of plasticized poly(l-lactide)

Many structural materials (metal alloys, polymers, minerals, etc.) are formed by quenching liquids into crystalline solids. This highly nonequilibrium process often leads to polycrystalline growth patterns that are broadly termed "spherulites" because of their large-scale average spherical shape. Despite the prevalence and practical importance of spherulite formation, only rather qualitative concepts of this phenomenon exist. It is established that phase field methods naturally account for diffusional instabilities that are responsible for dendritic single-crystal growth. However, a generalization of this model is required to describe spherulitic growth patterns, and in the present paper we propose a minimal model of this fundamental crystal growth process. Our calculations indicate that the diversity of spherulitic growth morphologies arises from a competition between the ordering effect of discrete local crystallographic symmetries and the randomization of the local crystallographic orientation that accompanies crystal grain nucleation at the growth front [growth front nucleation (GFN)]. This randomization in the orientation accounts for the isotropy of spherulitic growth at large length scales and long times. In practice, many mechanisms can give rise to GFN, and the present work describes and explores three physically prevalent sources of disorder that lead to this kind of growth. While previous phase field modeling elucidated two of these mechanisms--disorder created by particulate impurities or other static disorder or by the dynamic heterogeneities that spontaneously form in supercooled liquids (even pure ones)--the present paper considers an additional mechanism, crystalline branching induced by a misorientation-dependent grain boundary energy, which can significantly affect spherulite morphology. We find the entire range of observed spherulite morphologies can be reproduced by this generalized phase field model of polycrystalline growth.

/pdf/growth-and-form-of-spherulites-38blbzd6m8.pdf

Growth and form of spherulites.

Microporous membrane formation via thermally-induced phase separation.

A systematic study of impurity segregation in spherulitic crystallization is described. The experiments deal principally with high polymers, in which the role of ``impurities'' is fulfilled by stereoirregular molecules or by molecules of low molecular weight. It is shown that these species are rejected preferentially by growing crystals and that their diffusion plays a vital part in governing over‐all morphology. In particular, openness of texture is related to the concentration of impurity present; and coarseness of texture, which is a measure of the ``diameters'' of crystalline fibers between which impurities become concentrated during crystallization, is determined by δ=D/G, where D is the diffusion coefficient in the melt and G is the radial growth rate of the spherulite. Results provide substantial support for a theory of spherulitic crystallization proposed by the authors.

Spherulitic Crystallization from the Melt. I. Fractionation and Impurity Segregation and Their Influence on Crystalline Morphology

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

H. D. Keith

Author Tools

Chat about Author

Papers

Spherulitic Crystallization from the Melt. I. Fractionation and Impurity Segregation and Their Influence on Crystalline Morphology