Crystallization Behavior and Structural Properties of Model Semicrystalline Polyolefins

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The main objective of this research proposal is to improve understanding of thethermodynamic, kinetic and structural properties of non-oriented bulk crystallizedflexible chain polymers. Building on a foundation that established the importantindependent structural variables that describe the crystalline state, and final properties, aresearch program is described to advance the understanding of the interplay betweenchain microstructure, phase structure, crystallization kinetics and morphology of thedominant class of crystalline polymers, the polyolefins. Emphasis is given to novelstudies of model branched polyethylenes that serve as control microstructures to establishthe connection between molecular architecture and the semicrystalline morphology thatthey assemble. Two sets of model branched polyethyelenes will be studied. One set ofprecisely spaced branched polyethylenes serve as a bridge between the crystallization ofshort-chain molecules and the more complex behavior of industrial-like linear lowdensity polyethylenes. The second set of model long chain-branched (LCB) randomethylene copolymers will provide fundamentals for the effect of length and architectureof LCB on the crystallization behavior of these polyethylenes from isotropic melts,before additional effects intrinsic to flow, come into play. Details of the early stages ofthe crystallization of these systems serve as a basis to describe the properties of H-linkand other types of LCB poly(propylenes) also subjects of study in this proposal.The work on model systems will provide an opportunity for faculty and studentsof the University of Florida and the FAMU-FSU College of Engineering to interactclosely toward integrating catalysis, macromolecular architecture and their path to theordered state beyond each group's laboratory boundaries.The proposal also includes detailed work to substantiate a model of defectmicrostructure for Z-N based isotactic poypropylenes, derived from previous studies, aswell as a continuation of the crystallization behavior of metallocene random propylenecopolymers. In this venue emphasis is given to integrate the dynamics of thepolymorphic behavior in the analysis of the overall crystallization and the linear growthrates of these copolymers. The FAMU-FSU College of Engineering is a jointly managed program of theFlorida State University, a Research I institution with an enrollment of 38,000 andFlorida A&M University, a historically Black University with an enrollment of 12,000.Faculty hold joint appointments at both institutions, and students from both universitiesenroll in the same engineering classes. The present enrollment at the College ofEngineering consists of approximately 50% minority students and over 25% women,making it unique in a number of respects. The proposed work includes activeparticipation of graduate and undergraduate students and training in current techniques ofcharacterization of polymers. These activities parallel the commitment of the PI toeducation of students in the area of Polymer Science and Engineering.