Abstract/Details

Studies on the stability and intermolecular interactions of cellulose and polylactide systems using molecular modeling


2006 2006

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Abstract (summary)

The stability and intermolecular interactions of cellulose and polylactide (PLA) systems were studied using molecular modeling.

This work explains how grafting various groups onto cellulose increases hydrolysis of the glycosidic linkages of cellulose. A substituent increases hydrolysis of cellulose by serving as an anchor to the end of the cleaved cellulose to which it is bonded, making it less mobile, and allowing it to have stronger interactions than those in pure hydrolyzed cellulose. Hydrolysis increases with the size of the substituent. Molecules sorbed but not grafted to cellulose do not increase hydrolysis. Hydrolysis mainly occurs at glucoses bonded to the substituent. A substituent on the sixth carbon position of cellulose increases hydrolysis to a greater extent than does one on the second or third carbon position.

The effect of blending poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) and the effect of various arrangements of L-lactide and D-lactide in poly(L-lactide-co-D-lactide) on the resistance of polylactide (PLA) to hydrolysis has been explained. Among the homopolymer blends, the 50/50 PLLA/PDLA blend has the greatest resistance to hydrolysis due to its having stronger hydrogen-bonding and van der Waals forces than pure PLLA or PDLA. The change in potential energy for hydrolysis decreases linearly with increasing % PLLA or % PDLA from 0 to 50%. Among the copolymers containing a given percentage of L-lactide and D-lactide, those containing longer blocks of L-lactide and D-lactide have greater resistance to hydrolysis compared to those with shorter blocks or random copolymers because copolymers with longer blocks are more stable before hydrolysis compared to the other copolymers. Among the copolymers with long blocks of L- and D-lactide, those containing 50% L-lactide have a greater resistance to hydrolysis compared to the copolymers with 26% or 74% L-lactide. Blends or copolymers that are mirror images of each other have the same resistance to hydrolysis.

The effect of the structure of a molecule on its ability to adsorb onto PLA has been explained. The adsorbate-PLA interaction energies calculated for various disperse dyes and drugs agree with experimental data for their percent sorption onto PLA.

Indexing (details)


Subject
Polymers;
Materials science;
Textile research
Classification
0495: Polymers
0794: Materials science
0994: Textile research
Identifier / keyword
Applied sciences, Pure sciences, Cellulose, Molecular modeling, Polylactide, Stability
Title
Studies on the stability and intermolecular interactions of cellulose and polylactide systems using molecular modeling
Author
Karst, David T.
Number of pages
100
Publication year
2006
Degree date
2006
School code
0138
Source
DAI-B 67/10, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780542908705
Advisor
Yang, Yiqi
University/institution
The University of Nebraska - Lincoln
University location
United States -- Nebraska
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3237059
ProQuest document ID
305272905
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305272905
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