Molar mass determination of microwave initiated polycondensation produced PLLA by capillary viscometry method

Abstract

The microwave initiated polycondensation is a new approach for polylactic acid production. The time need of this process is quite less compared to the standard polycondensation process, but the progress and improvement of the molar mass is the most important basic factor. In my earlier work the standard polycondensation has already been investigated, so to be able to compare both methods PLLA has been produced by microwave initiated polycondensation too. The measurement of molar weights is a crucial point of polymer synthesis. According to my earlier work a rheology-based method was used again to define the molar masses during the polymerization process and make the comparison reliable. During my experiments PLLA has been synthesized by microwave initiated polycondensation method. According to the relevant literature, by standard polycondensation 104-105 g•mol-1 molar mass can be reached, so the main question was that how long should be the microwave process run to result the same level of molar mass. During the experiments PLLA samples have been taken according to a special time plan, then solved in chloroform prepared samples with different concentrations for further analysis. To measure the flow-times Ubbelohde capillary viscometer was applied at this time too. Based on the data of viscometry measurements the intrinsic viscosities have been graphically defined then the molar masses of polylactic acid polymers were calculated according to the correlation of Mark - Houwink relation.