Total for the last 12 months
number of access : ?
number of downloads : ?
ID 115689
Author
Suganuma, Koto Teijin
Asakura, Tetsuo Tokyo University of Agriculture and Technology
Cheng, H. N. USDA Agricultural Research Service
Keywords
Bernoullian
NMR
poly(lactic acid)
statistical model
stereosequences
tacticity
Content Type
Journal Article
Description
The physical properties of poly(lactic acid) (PLA) are influenced by its stereoregularity and stereosequence distribution, and its polymer stereochemistry can be effectively studied by NMR spectroscopy. In previously published NMR studies of PLA tacticity, the NMR data were fitted to pair-addition Bernoullian models. In this work, we prepared several PLA samples with a tin catalyst at different L,L-lactide and D,D-lactide ratios. Upon analysis of the tetrad intensities with the pair-addition Bernoullian model, we found substantial deviations between observed and calculated intensities due to the presence of transesterification and racemization during the polymerization processes. We formulated a two-state (pair-addition Bernoullian and single-addition Bernoullian) model, and it gave a better fit to the observed data. The use of the two-state model provides a quantitative measure of the extent of transesterification and racemization, and potentially yields useful information on the polymerization mechanism.
Journal Title
Polymers
ISSN
20734360
Publisher
MDPI
Volume
11
Issue
4
Start Page
725
Published Date
2019-04-19
Rights
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
EDB ID
DOI (Published Version)
URL ( Publisher's Version )
FullText File
language
eng
TextVersion
Publisher
departments
Science and Technology