Unusual Temperature Dependence of the Crystal Growth Rates of Bromine Substituted Polyethylenes

• Other Authors: Zhang, Wei (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Chemical engineering; Biomedical engineering
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-8516

ABSTRACT Precisely halogenated polyethylenes are unique polyolefins with a halogen placed on and every "n" number of backbone carbons. Contrasting random analogs, these systems are highly crystalline developing spherulitic morphologies due to a crystallization pattern similar to that of a homopolymer chain. The halogen is accommodated in the crystalline regions as a defect that strains the chain packing proportionally to the van der Waals radius of the halogen. The present work studies the temperature dependence of the linear growth rates of a bromine substituted polyethylenes on each and every 9th, 15th, 19th and 21st backbone carbon. The linear growth rates display a discrete minimum with decreasing temperature at a critical crystallization temperature which is reminiscent of the minimum in crystallization rate observed in long chain n-alkanes. The spherulitic morphology and overall positive birefringence remains unchanged. The minimum in growth rate is analyzed on the basis of self-poisoning at the growth front resulting from frequent but unstable disordered chains depositions that accommodate the Br atoms. === A Thesis submitted to the Department of Chemical and Biomedical Engineering in partial fulfillment of the requirements for the degree of Master of Science. === Spring Semester, 2013. === March 27, 2013. === bromine substituted polyethylenes, crystallization, growth rates === Includes bibliographical references. === Rufina G. Alamo, Professor Directing Dissertation; Theo M. Siegrist, Committee Member; Anant Paravastu, Committee Member.