Molecular and bulk characterization of PLA and PLGA samples using multi-detector GPC and rheometry

Poly(lactic acid) is a biodegradable polymer derived from natural resources (corn starch), that has received significant attention in recent years.  It is one of the most prevalent biodegradable polymers in the market place due to availability, low cost of production, and when derived from natural sustainable sources it is a truly renewable polymer.  PLA is often used as a copolymer with glycolic acid to form PLGA and is routinely used with varying compositions of lactic and glycolic acids.  Being a versatile polymer, it is used in a wide variety of applications from additive manufacture (3D printing) to disposable cutlery, biodegradable sutures, drug delivery, or as biodegradable packaging.

It is widely recognized that the bulk properties of polymers are strongly dependent on their molecular properties.  Most commonly, the strongest determinant of a polymer’s strength is assumed to be its molecular weight.  However, in copolymers such as PLGA, it is also likely that copolymer composition will also strongly affect those properties.

This application note uses two Malvern technologies to explore the relationship between the molecular and bulk properties of PLA and PLGA.  Multi-detector GPC is used to measure molecular weight and intrinsic viscosity (which is dependent on copolymer composition), while rotational rheology is used to study melt-viscosity.  The two results are then compared to study which molecular properties best correlate with melt-viscosity.

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