Publication:
Effects of Molecular Architecture on Crystallization Behavior of Pol(lactic Acid) and Ethylene-Vinyl Acetate

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dc.contributor.advisorShaw Ling Hsu
dc.contributor.advisorScott M. Auerbach
dc.contributor.advisorSamuel P. Gido
dc.contributor.authorKalish, Jeffrey Paul
dc.contributor.departmentUniversity of Massachusetts Amherst
dc.date2023-09-23T04:50:40.000
dc.date.accessioned2024-04-26T19:49:51Z
dc.date.available2024-04-26T19:49:51Z
dc.date.issued2011-09-01
dc.description.abstractThe relationship between polymer chain architecture, crystallization behavior, and morphology formation was investigated. The structures formed are highly dependent on chain configuration and crystallization kinetics. Poly(lactic acid) (PLA) and Poly(ethylene-co-vinyl acetate) (EVA) random copolymers were studied. Sample characterization was performed using a variety of techniques, including spectroscopy, scattering, and calorimetry. In PLA, structural differences between α’ and α crystalline phases were analyzed using cryogenic infrared and Raman spectroscopy. Compared to the  crystal, the ’ crystal has slightly looser packing and weaker intermolecular interactions involving carbonyl and methyl functional groups. Simulations in conjunction with Raman scattering analyzed the conformational distortion of the α’ phase. The conformation of an α’ chain was determined to have tg’t-103 conformation with tg’t-31 units randomly distributed along the chain. Departure of the O-C α dihedral angle was also confirmed. The structural disorder leads to different thermal properties for α’ and α crystalline forms, which was quantified by measuring the enthalpic change at melting for both crystals ( = 57 ± 3 J/g and =9 6 ± 3 J/g). The transformation from α’ to α and the mechanism of order formation in PLA were also elucidated. The relationship between chain configuration of EVA random copolymers and crystallization behavior was established. For three different EVA samples, the distribution of methylene sequences was calculated and compared to a distribution of crystallite sizes formed. This comparison revealed that only a small fraction of the total methylene segments present actually crystallized. Cocrystallization with highly mobile oligomers was explored to enhance the crystallization of EVA copolymers. When blended, EVA28 (28 weight percentage) cocrystallizes with C36H74 n-alkane resulting in faster crystallization kinetics and a higher degree of crystallinity. The observed increase in degree of crystallinity was directly related to the chain configuration. Compositional mapping using Raman spectroscopy provided evidence for oligomer nucleation. The cocrystallization kinetics and morphology of EVA and n-alkane blends was found to depend on the chain length of oligomer. In both systems studied, crystallization kinetics determines the morphologies formed, which are undoubtedly related to the details of molecular architecture.
dc.description.degreeDoctor of Philosophy (PhD)
dc.description.departmentPolymer Science and Engineering
dc.identifier.doihttps://doi.org/10.7275/2389682
dc.identifier.urihttps://hdl.handle.net/20.500.14394/38901
dc.relation.urlhttps://scholarworks.umass.edu/cgi/viewcontent.cgi?article=1464&context=open_access_dissertations&unstamped=1
dc.source.statuspublished
dc.subjectcrystallization
dc.subjectpoly(ethylene-co-vinyl acetate)
dc.subjectpoly(lactic acid)
dc.subjectpolymer structure
dc.subjectpolymorphism
dc.subjectthermal properties
dc.subjectMaterials Science and Engineering
dc.titleEffects of Molecular Architecture on Crystallization Behavior of Pol(lactic Acid) and Ethylene-Vinyl Acetate
dc.typedissertation
dc.typearticle
dc.typedissertation
digcom.contributor.authorisAuthorOfPublication|email:jeff.kalish@gmail.com|institution:University of Massachusetts Amherst|Kalish, Jeffrey Paul
digcom.identifieropen_access_dissertations/454
digcom.identifier.contextkey2389682
digcom.identifier.submissionpathopen_access_dissertations/454
dspace.entity.typePublication
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