Structural characterisation of naturally occuring trans-polyisoprenes

Boochathum P., . and Mori M., . and Sato Y., . and Tanaka Y., . and Takei A., . Structural characterisation of naturally occuring trans-polyisoprenes. pp. 241-245. ISSN 0127-7065

The structure of trans-polyisoprene isolated from Chicle latex and Gutta percha latex was analysed by 13C-NMR spectroscopy. The trans-polyisoprene from Chicle latex showed the 13C-NMR signals characteristic of the dimethylallyl terminal unit (w-terminal) and trans-isoprene unit terminated with hydroxyl and ester groups (a-terminal). The ester terminal group was not detected in the trans-polyisoprene from Chicle resin. The degree of polymerisation estimated from the intensity ratio of the signals from internal trans units and w-terminal group was in fair agreement with the value obtained by GPC-LALLS measurement. However the intensity ratio of signals from the w-terminal and a-terminal groups was found to be 1/0.76 indicating the loss of a part of a-terminal in the latex sample. The trans-polyisoprene from Gutta percha latex showed a similar 13C-NMR spectrum as that from Chicle. The loss of the a-terminal was also observed for the trans-polyisoprene from Gutta percha latex. It was presumed that a chemical or biochemical modification of a-terminal groups occurred during storage of the latex.

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Abstract

The structure of trans-polyisoprene isolated from Chicle latex and Gutta percha latex was analysed by 13C-NMR spectroscopy. The trans-polyisoprene from Chicle latex showed the 13C-NMR signals characteristic of the dimethylallyl terminal unit (w-terminal) and trans-isoprene unit terminated with hydroxyl and ester groups (a-terminal). The ester terminal group was not detected in the trans-polyisoprene from Chicle resin. The degree of polymerisation estimated from the intensity ratio of the signals from internal trans units and w-terminal group was in fair agreement with the value obtained by GPC-LALLS measurement. However the intensity ratio of signals from the w-terminal and a-terminal groups was found to be 1/0.76 indicating the loss of a part of a-terminal in the latex sample. The trans-polyisoprene from Gutta percha latex showed a similar 13C-NMR spectrum as that from Chicle. The loss of the a-terminal was also observed for the trans-polyisoprene from Gutta percha latex. It was presumed that a chemical or biochemical modification of a-terminal groups occurred during storage of the latex.

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Item Type:	Article
AGROVOC Term:	Latex
AGROVOC Term:	Rubber
AGROVOC Term:	NMR spectroscopy
AGROVOC Term:	Isolation techniques
AGROVOC Term:	Biosynthesis
AGROVOC Term:	Hydroxylation
AGROVOC Term:	Storage
AGROVOC Term:	Polymerization
AGROVOC Term:	Molecular weight
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	24 Apr 2025 06:28
URI:	http://webagris.upm.edu.my/id/eprint/23510

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