Method for preparing microparticles having a selected polymer molecular weight

Abstract

A method for preparing microparticles having a selected polymer molecular weight. The hold time and temperature of a solution containing a nucleophilic compound and a polymer having a starting molecular weight are controlled in order to control the molecular weight of the polymer in the finished microparticle product. In this manner, a selected polymer molecular weight in the finished microparticle product can be achieved from a variety of starting material molecular weights.

1 . A method of controlling the molecular weight of a polymer forming a microparticle, comprising: 
 (a) preparing a first phase, the first phase comprising a biodegradable polymer having a starting molecular weight in the range of from 5 to 500 kD, a solvent for the polymer, and a nucleophilic compound which catalyses ester hydrolysis of the biodegradable polymer;    (b) maintaining the first phase at a hold temperature for a hold period prior to step (c);    (c) combining the first phase with a second phase in a static mixer to form an emulsion; and    (d) combining the emulsion and an extraction medium, thereby forming microparticles;    wherein the hold temperature and the hold period are modified to allow the starting molecular weight of the polymer to reduce by an amount in the range of from 10 to 50% to the molecular weight of the polymer forming the microparticles.