Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307504
Title: The synthesis of novel biodegradable polyesters and copolyesters from anhydrosulfites
Author: N'Goala, Karine L. R.
ISNI:       0000 0001 3438 7651
Awarding Body: Aston University
Current Institution: Aston University
Date of Award: 1996
Availability of Full Text:
Access through EThOS:
Access through Institution:
Abstract:
This thesis was concerned primarily with the synthesis and the ring-opening polymerisation of anhydrosulfites (1,3,2-dioxa-thiolan-4-one-2-oxides), and secondly with the copolymerisation of anhydrosulfites with -caprolactone. The polyesters and copolyesters synthesised are of considerable interest in medical applications and also for use as environmental friendly packaging. A range of anhydrosulfites were prepared according to an established method. Aliphatic anhydrosulfites were obtained with a level of purity satisfactory for polymerisation whereas aromatic anhydrosulfites decomposed during distillation and purification by chromatographic techniques. Aliphatic anhydrosulfites with a substituent, such as methyl, isopropyl, n-butyl and isobutyl were studied by NMR spectroscopy. Analysis of these spectra revealed that the five-membered anhydrosulfite ring was puckered and that when the substituent was bulky, rotations about the alkyl chains were restricted. A wide range of anionic initiators may be used to initiate anhydrosulfites. Lithium alkyls turned out to be more successful than alkali metal alkoxides and amides. The molecular weights were found to depend on the basicity of the initiator, the monomer-to-initiator ratio, the nature of the solvent and the polymerisation temperature. The molecular weight n of poly(L-lactic acid) ranged from (0.5 to 6)x104. Highly crystalline and purely isotactic poly(lactic acid) was synthesised from L-lactic acid anhydrosulfite (L-LAAS) whereas DL-LAAS led to an amorphous polymer with randomly distributed D-and L-lactic units. This indicated that this polymerisation was not stereoselective. However, the bulkiness of the substituent in the anhydrosulfites molecule was found to influence the stereoselectivity of the polymerisation, thus polyesters with isobutyl or n-butyl pendant group were preferentially isotactic. Block-copolymers of -caprolactone and several anhydrosulfites were successfully produced. Block-copolymers of LAAS with -caprolactone were also synthesised, but the incorporation of caprolactone units was rather small. In contrast, random copolymerisation of LAAS and -caprolactone led to polymers with blocky structures similar to those obtained in the block-copolymerisation of LAAS with -caprolactone.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Phd
EThOS ID: uk.bl.ethos.307504  DOI: Not available
Keywords: Chemical Engineering ; Applied Chemistry ; Chemical Engineering Chemical engineering
Share: