Poly(lactic acid) microcapsules: Tailoring properties via solid state polymerization

Chronaki, Konstantina; Korres, Dimitrios; Papaspyrides, Constantine; Vouyiouka, Stamatina

doi:10.1016/j.polymdegradstab.2020.109283

Cited by 15 publications

(12 citation statements)

References 50 publications

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“…However, in order to produce polyesters suitable for films, fibers, or bottles, it is mandatory to obtain high molecular weight materials. A very successful method that has been applied in industrial polymers to increase the molecular weight is solid state polymerization (SSP) [10], which found success with polyesters like PET [11][12][13][14][15] and PLA [16][17][18]. Nevertheless, there is a limited number of studies concerning the application of SSP on furan-based polymers.…”

Section: Introductionmentioning

confidence: 99%

Towards High Molecular Weight Furan-Based Polyesters: Solid State Polymerization Study of Bio-Based Poly(Propylene Furanoate) and Poly(Butylene Furanoate)

et al. 2020

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In the era of polymers from renewable resources, polyesters derived from 2,5 furan dicarboxylic acid (FDCA) have received increasing attention due to their outstanding features. To commercialize them, it is necessary to synthesize high molecular weight polymers through efficient and simple methods. In this study, two furan-based polyesters, namely poly (propylene furanoate) (PPF) and poly(butylene furanoate) (PBF), were synthesized with the conventional two-step melt polycondensation, followed by solid-state polycondensation (SSP) conducted at different temperatures and reaction times. Molecular weight, structure and thermal properties were measured for all resultant polyesters. As expected, increasing SSP time and temperature results in polymers with increased intrinsic viscosity (IV), increased molecular weight and reduced carboxyl end-group content. Finally, those results were used to generate a simple mathematical model that prognosticates the time evolution of the materials’ IV and end groups concentration during SSP.

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Section: Introductionmentioning

confidence: 99%

Towards High Molecular Weight Furan-Based Polyesters: Solid State Polymerization Study of Bio-Based Poly(Propylene Furanoate) and Poly(Butylene Furanoate)

et al. 2020

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“…In support to our interpretation, Pfaendner et al studied different PLA grades with and without additives and recorded reorganization of crystals (metastable crystals changing to thicker or of better quality ones) upon involvement of SSP; thus, they concluded that SSP may serve as a further crystallization step. Also, in a similar connection, Chronaki et al reported that the effectiveness of SSP on increasing M v and CF drops with increasing M v of initial PLA or when SSP is employed on MCs.…”

Section: Resultsmentioning

confidence: 80%

“…The average size of the spherical MCs is 2.8 μm, 27 while small numbers of MCs vary in size, both smaller and larger, as can be seen in Figure 1b. The size distribution was reported in a recent work by Chronaki et al 27 to be 0.4−22 μm for MCs and 0.4−48 μm for MC-SSP. The MCs under investigation target at both short-and large-scale applications (adhesives, cosmetics, pharmaceutics, industry), involving, for example, the encapsulation of active compounds and their long/short-time release (slow/fast).…”

Section: Methodsmentioning

confidence: 92%

Effects of High Crystallinity on the Molecular Mobility in Poly(lactic acid)-Based Microcapsules

Klonos,

Chronaki,

Vouyiouka

et al. 2024

ACS Appl. Polym. Mater.

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We investigate the molecular mobility in biodegradable poly(lactic acid) (PLA) in the thin shell of spherical hollow semicrystalline microcapsules (MCs), of remarkable crystalline fractions, CFs (>55%). The effect of the solid-state polymerization (SSP) on MCs as a post-encapsulation modification is additionally studied. For comparison to MCs, we study the corresponding precursor linear polylactides, of low molecular weight, M v ∼20 kg/ mol, and high CF. The emphasis is given on the static and dynamic glass transition and their dependence on crystallinity. To these aims, we employed broad-band dielectric spectroscopy and differential scanning calorimetry, supplemented by X-ray diffraction. Compared with initial untreated semicrystalline PLA with CF ∼42 wt %, the segmental polymer dynamics (T g and α relaxation) is significantly faster in all treated samples and exhibits strongly suppressed cooperativity, which is shown here for the first time. The thermochemical treatments, hydrolysis and thermal annealing, of pure PLA result in a particular semicrystalline morphology of PLA in MCs and their precursors, severely affecting the glass-transition dynamics. The overall recordings indicate that the mobile amorphous polymer chains, i.e., rather short chains emerging from the crystals, in the micrometric MC shell suffer strong spatial constraints and nanoconfinement by large numbers of nanosized crystals upon all treatments. The additional employment of SSP increases the chains' M v of only the amorphous polymer part, increases CF by ∼10%, and, surprisingly, "loosens" the nanoconfinement on the amorphous polymer chains between crystals. This is probably due to a reorganization of the crystalline domains. Overall, the results reveal the potential for manipulation of CF (up to very high amounts approaching ∼80%) and of semicrystalline morphology. This, subsequently, enables the tuning of barrier properties (permeability), heat transport, and mechanical performance of PLA, being actually desired, as the said PLA MCs are envisaged for use in applications involving active substance-controlled release.

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“…In recent years, several groups of researchers have reported the preparation of polylactide microcapsules containing different drugs and studied the effects of manufacturing parameters on the microcapsule's characteristics. In the study reported by Chronaki et al, microcapsules of PLA of different molecular weights were created through solid-state polymerization (SSP), evaluating the efficiency of this technique as a postencapsulation modification step [123]. Initially, PLA microcapsules were prepared by double emulsion-solvent evaporation and then subjected to SSP in a fixed bed reactor under nitrogen flow, causing postpolymerization reactions in the polymeric walls.…”

Section: (B) Poly(lactic Acid)mentioning

confidence: 99%

Biodegradable Polymers for Microencapsulation Systems

Parente

Sousa

Marques

et al. 2022

Advances in Polymer Technology

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Environmentally friendly alternatives have become sought after upon the development of scientific research and industrial processes. Recent trends suggest biodegradable polymers as the most promising solution for synthetic microcapsule systems. Safety, efficiency, biocompatibility, and biodegradability are some of the properties that biodegradable systems in microencapsulation can provide for a broad spectrum of applications. The controlled release of encapsulated active agents is a research field that, over the years, has been constantly innovating due to the promising applications in the areas of pharmaceutical, cosmetic, textile industry, among others. This article presents an overview of different polymers with potential for microcapsule synthesis, namely, biodegradable polymers. First, natural polymers are discussed, which are divided into two categories: polysaccharide-based polymers (cellulose, starch, chitosan, and alginate) and protein polymers (gelatin). Second, synthetic polymers are described, where biodegradable polymers such as polyesters, polyamides, among others appear as examples. For each polymer, this review presents its origin, relevant properties, applications, and examples found in the literature regarding its use in biodegradable microencapsulation systems.

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Poly(lactic acid) microcapsules: Tailoring properties via solid state polymerization

Cited by 15 publications

References 50 publications

Towards High Molecular Weight Furan-Based Polyesters: Solid State Polymerization Study of Bio-Based Poly(Propylene Furanoate) and Poly(Butylene Furanoate)

Towards High Molecular Weight Furan-Based Polyesters: Solid State Polymerization Study of Bio-Based Poly(Propylene Furanoate) and Poly(Butylene Furanoate)

Effects of High Crystallinity on the Molecular Mobility in Poly(lactic acid)-Based Microcapsules

Biodegradable Polymers for Microencapsulation Systems

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