Premium
A novel method to determine the molecular weight of the oligomers of biodegradable polymer
Author(s) -
Maniar Manoj L.,
Advant Siddharth J.,
Kalonia Devendra S.,
Simonelli Anthony P.
Publication year - 1992
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1992.220030604
Subject(s) - hydrolysis , polymer , reaction rate constant , monomer , catalysis , materials science , base (topology) , ionic strength , polymer chemistry , chemistry , organic chemistry , kinetics , aqueous solution , mathematical analysis , physics , mathematics , quantum mechanics
The biodegradable polymers used in controlled release applications are primarily insoluble polymers which undergo chemical or enzymatic hydrolysis to form soluble monomeric or oligomeric units. To determine the endurance of the polymer after implantation or injection into the body it is important to determine the rate of elimination of the intermediates formed upon the hydrolysis of the polymer. It is essential to identify these intermediates before its elimination rate can be determined. Identification of these intermediates is a problem because they are difficult to isolate, and are thermally and hydrolytically unstable. A new technique is proposed, taking advantage of the neighboring group effect on the hydrolysis of ionic and non‐ionic oligomers, to determine the molecular weight of unknown species that are formed upon hydrolysis of the polymer. The technique involves the determination of the specific acid and base catalytic rate constants. To demonstrate the technique, a time sequence synthesis was carried out to synthesize several oligomers that would be forming upon the hydrolysis of poly(butylene tartrate). Hydrolysis studies were conducted with these oligomers and the samples were analyzed by liquid chromtography. The observed rate constant for the hydrolysis under acidic and alkaline pH medium were calculated from the terminal slopes of the first order plot. The observed rate constants were further utilized to calculate the specific acid and base catalytic rate constants. These specific rate constants, along with the micro‐hydrogen and ‐hydroxyl ion catalytic rate constants, were used to determine the molecular weight of the intermediate species. The molecular weight obtained from the kinetic parameters was in excellent agreement with the results obtained from fast atom bombardment mass spectrometry. The same type of analysis can be extended to any multifunctional group compound which has repeat units and can undergo a specific reaction which can be accurately measured.