PLGA Barrier Materials from CO₂. The influence of Lactide Co-monomer on Glycolic Acid Polyesters

Abstract

The combination of the predicted polymer market growth and the emergence of renewable feedstocks creates a fantastic opportunity for sustainable polymers. To replace fossil-based feedstock, there are only three alternative sustainable carbon sources: biomass, CO 2 , and existing plastics (via mechanical and/or chemical recycling). The ultimate circular feedstock would be CO 2 : it can be electrochemically reduced to formic acid derivatives that subsequently can be converted into useful monomers such as glycolic acid. This work is part of the European Horizon 2020 project “Ocean” in which the steps from CO 2 to glycolic acid are developed. Polyglycolic acid (PGA) and poly(lactide- co -glycolide) (PLGA) copolyesters with high lactic acid (LA) content are well-known. PGA is very difficult to handle due to its high crystallinity. On the other hand, PLGAs with high LA content lack good oxygen and moisture barriers. The aim of this work is to understand the structure–property relationships for the mostly unexplored glycolic acid rich PLGA copolymer series and to assess their suitability as barrier materials. Thus, PLGA copolymers with between 50 and 91 mol % glycolic acid were synthesized and their properties were evaluated. Increased thermal stability was observed with increasing glycolic acid content. Only those containing 87 and 91 mol % glycolic acid were semicrystalline. A crystallization study under non-isothermal conditions revealed that copolymerization reduces the crystallization rate for PLGA compared to polylactic acid (PLA) and PGA. While PGA homopolymer crystallizes completely when cooled at 10 °C·min –1 , the copolymers with 9 and 13% lactic acid show almost 10 times slower crystallization, which is a huge advantage vis-à-vis PGA for processing. The kinetics of this process, modeled with the Jeziorny-modified Avrami method, confirmed those observations. Barrier property assessment revealed great potential for these copolymers for application in barrier films. Increasing glycolic acid content in PLGA copolymers enhances the barrier to both oxygen and water vapor. At room temperature and a relative humidity below 70% the PLGA copolymers with high glycolic acid content outperform the barrier properties of polyethylene terephthalate.

An overview of biodegradable packaging in food industry

“… 16 20–25 700–800 250–300 58–60 Jost (2018) ; Rosa et al (2004) PGA Mainly used as copolymer-PGLA because PGA alone is insoluble in most organic solvents and brittle in nature has limited its alone application. 13 10 1 40 220–230 Samantaray et al (2020) ; Murcia et al (2020) PBS It has great compatibility with fibers so for food application films are made using a blend with different fibers like jute, cellulose etc 40 2200–2300 1.72–2.00 150 90–120 Messin et al (2020) PHB Stiff and brittle, known for its UV resistivity property. Its mechanical and physical property are same as that of isostatic PP 25 1.16 183 5 180 Ivankovic et al (2017) CPLA Products form CPLA can withstand high temperature without deforming.…”

Biocompatible Light Guide‐Assisted Wearable Devices for Enhanced UV Light Delivery in Deep Skin

“…In the current process, the PLGA melts and partially crystallizes, to yield semicrystalline states after cooling to room temperature. [ 40 ] This state results in mechanically robust microneedles for skin penetration, but with a base layer that does not offer sufficient flexibility to conform to curved regions of the skin. A scheme to overcome this limitation involves treating the base layer (≈0.2 mm in thickness) with solvents such as ethyl acetate (as drops or in vapor form) without exposing the microneedles (see the Experimental Section).…”

Synthesis of Poly(Lactic Acid-co-Glycolic Acid) Copolymers with High Glycolide Ratio by Ring-Opening Polymerisation

“…Poly(lactic acid- co -glycolic acid) (PLGA) is a common copolymer that has found widespread commercial use in biomedical devices. PLGAs with high glycolide contents possess PGA’s high barrier properties and tensile strength, whilst having lower melting temperatures so they can be processed at lower temperatures [ 13 ]. Due to their reduced hydrophobicity and crystallinity in comparison to PLA, PLGAs display much faster biodegradation, whilst maintaining similar mechanical properties to PLA [ 7 ].…”

“…By adapting PLGA production processes towards those used for packaging grade PLA, high barrier biodegradable PLGA packaging materials may be produced. Furthermore, the cost of PLGA may decline as a result of the development of new synthetic routes towards glycolic acid [ 13 , 15 , 16 ].…”

“…This L:G composition was selected as it is high in glycolide content whilst still being an amorphous material, which results in transparent products. Once the lactide percentage falls below 15%, the copolymer becomes semicrystalline and has a T m of about 190 °C [ 13 ]. All PLGAs in this study were synthesised by the ROP of glycolide and d - l -lactide using tin 2-ethylhexanoate (Sn(Oct) 2 ) as the catalyst and 1-dodecanol as the initiator.…”