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)

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“…Encapsulation systems are being constantly developed for three main purposes pertaining to the active compound: (i) shielding of the active compound against environmental conditions such as pH, radiation, temperature and other chemicals, (ii) changing of its physicochemical properties and (iii) more facile and better controlled transfer of the compound to the target [ 1 , 2 , 3 , 4 , 5 , 6 ]. In particular, microcapsule-based encapsulation systems (MCs) consist of the core material and the surrounded shell, with sizes ranging from 1–1000 μm [ 7 , 8 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Polyamide-Based Microcapsules via Interfacial Polymerization: Effect of Key Process Parameters

et al. 2021

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Polyamide microcapsules have gathered significant research interest during the past years due to their good barrier properties; however, the potential of their application is limited due to the fragility of the polymeric membrane. Fully aliphatic polyamide microcapsules (PA MCs) were herein prepared from ethylene diamine and sebacoyl chloride via interfacial polymerization, and the effect of key encapsulation parameters, i.e., monomers ratio, core solvent, stirring rate and time during the polymerization step, were examined concerning attainable process yield and microcapsule properties (shell molecular weight and thermal properties, MC size and morphology). The process yield was found to be mainly influenced by the nature of the organic solvent, which was correlated to the diffusion potential of the diamine from the aqueous phase to the organic core through the polyamide membrane. Thus, spherical microcapsules with a size between 14 and 90 μm and a yield of 33% were prepared by using toluene as core solvent. Milder stirring during the polymerization step led to an improved microcapsule morphology; yet, the substantial improvement of mechanical properties remains a challenge.

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Section: Introductionmentioning

confidence: 99%

Synthesis of Polyamide-Based Microcapsules via Interfacial Polymerization: Effect of Key Process Parameters

et al. 2021

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

Cited by 15 publications

References 50 publications

Synthesis of Polyamide-Based Microcapsules via Interfacial Polymerization: Effect of Key Process Parameters

Synthesis of Polyamide-Based Microcapsules via Interfacial Polymerization: Effect of Key Process Parameters

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

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