Can a combination of poly(ethylene glycol) and dense phase carbon dioxide improve processing of polylactide? A high pressure rheology investigation

Abstract

High temperature melts or use of organic solvents are not practicable approaches for encapsulating protein based or thermally labile drugs into degradable polymers. Here, we demonstrate that poly(ethylene glycol) (PEG) in combination with supercritical carbon dioxide (scCO2) can dramatically reduce the viscosity of polymer melts allowing enhanced uptake of CO2 into poly(D,L-lactide) (PLA). Both PEG and CO2 are approved excipients in drug delivery and it is well documented that individually both are effective plasticisers. Using high pressure rheology techniques (scCO2 at 14 MPa) we demonstrate a synergistic impact leading to significantly lower processing temperatures with PEG employed as both a blended additive and as a component of a block copolymer.

Enhanced PET processing with organophosphorus additive: Flame retardant products with added-value for recycling

“…From various studies with supercritical fluids, it is known that an internal lubrication effect depends on molecular scale miscibility of the additive with the PET melt [60][61][62][63]. Therefore, the thermodynamic miscibility of DP molecules in PET melt was assessed at nanoscale utilizing dissipative particle dynamics (DPD).…”

“…It should be noted that in this work lubrication refers to an internal effect of DP molecules (lubricating macromolecules) and does not mean the lubrication of a polymer-surface contact. Thus, the desired effect of lubrication depends on a perfect mixing of additive and polymer on the length scale of their molecules [60][61][62][63]. As the mixing quality is improved on such fine length scales, the internal lubrication (of polymer molecular motions) becomes more efficient.…”

Interfacial stabilizing and reinforcing effects of silsesquioxane-based hybrid Janus molecules in extrusion supercritical CO2 foaming of polypropylene

“…In recent years, tougher environmental regulations spark renewed interest in supercritical carbon dioxide (scCO 2 ) foaming as CO 2 is non-toxic, nonflammable, and has relatively low environmental impact [6], better solubilities in polymers than other inert gases, and a critical point that is well within the processing windows of most foaming processes [7]. In addition, scCO 2 could act as a plasticiser to facilitate the flow of polymers in extruders [8]. Of the various scCO 2 foaming processes, extrusion foaming is commonly explored as it allows the foaming process to take advantage of the efficient heating and mixing, continuous processing, and high throughput features of an extruder.…”

Low-temperature and purification-free stereocontrolled ring-opening polymerisation of lactide in supercritical carbon dioxide

“…The resulting reduction in melt and glass transition temperatures and the lowering of polymer viscosity can bring many advantages, including facilitating low-temperature processing. [34][35][36][37] The use of scCO2 as the medium for a variety of polymerisations has been demonstrated, [38][39][40] including ROP of cyclic esters (including lactide) using both metal and organic catalysts. [41][42][43][44][45][46][47][48][49] These synthetic strategies have largely required lengthy reaction times (5 -24 h).…”