Transport of Small Molecules in Loaded Natural Rubber: Experimental Measurement and Numerical Simulation

Du, Ya; Mefford, O. Thompson

doi:10.1021/acsapm.2c01109

Cited by 4 publications

(14 citation statements)

References 63 publications

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“…The concentration of triacetin in the loaded sheets were determined by HS‐GC–MS as described in a previous work 12 . Briefly, a 3.2 mm diameter cylindric sample (∼7 mg) was punched out of the rubber sheet and placed in a 10 mL glass vial sealed by an aluminum cap and a silicone/PTFE septum.…”

Section: Experiments and Methodsmentioning

confidence: 99%

“…The release of triacetin from the loaded sheets can be mathematically modeled by Fickian diffusion equations (Equation to ): 12

\frac{\partial c}{\partial t} = D \frac{\partial^{2} c}{\partial x^{2}}, - L < x < L

t = 0, - L < x < L, c = c_{0}

t > 0, x = \pm L, - D \frac{\partial c}{\partial x} = k_{m} (c - {italicKc}_{italicext})

…”

Section: Experiments and Methodsmentioning

confidence: 99%

“…The concentration of triacetin in the loaded sheets were determined by HS-GC-MS as described in a previous work. 12 Briefly, a 3.2 mm diameter cylindric sample ($7 mg) was punched out of the rubber sheet and placed in a 10 mL glass vial sealed by an aluminum cap and a silicone/PTFE septum. The vial was incubated at 120 C for 15 min to achieve a distribution equilibrium of triacetin between the headspace and the sample.…”

Section: Quantitation Of Triacetin In Loaded Silicone Rubber Sheetsmentioning

confidence: 99%

“…10 Benefited from the unique molecular structures, silicone rubber demonstrates superior properties such as high permeability, flexibility, chemical inertness, biocompatibility, and wide range of working temperatures. 11 Physiochemical properties and compositions of the material systems, such as crosslink density [12][13][14][15][16][17][18][19] and concentration of the molecule [20][21][22][23] can affect the release of small molecules. External factors like mechanical strain may also affect the release and that is the focus of this work.…”

Section: Introductionmentioning

confidence: 99%

“…Physiochemical properties and compositions of the material systems, such as crosslink density 12–19 and concentration of the molecule 20–23 can affect the release of small molecules. External factors like mechanical strain may also affect the release and that is the focus of this work.…”

Section: Introductionmentioning

confidence: 99%

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Effects of uniaxial tensile strain on the release of small molecules from silicone rubber

Du,

Mefford

2023

J of Applied Polymer Sci

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Silicone rubber materials may be subject to mechanical strains which can affect the transport properties of small molecules loaded in the materials such as plasticizers and active molecules, hence deteriorating their intended mechanical properties or affecting their performance as carriers of active molecules. Therefore, it is important to understand the effects of mechanical strains on transport of small molecules in the silicone rubber matrix. In this work, silicone rubber sheets loaded with 2 wt% triacetin were stretched and held at four different lengths up to 125% engineering strain. The mass transfer coefficients and diffusion coefficients of triacetin in the strained silicone rubber were determined by monitoring the release of triacetin using headspace gas chromatography–mass spectrometry. It was found that there was no significant change of diffusion coefficient as the applied strain increased, which might result from two microstructure changes that had conflicting effects on diffusion: chain orientation and free volume deformation.

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Section: Experiments and Methodsmentioning

confidence: 99%

“…The release of triacetin from the loaded sheets can be mathematically modeled by Fickian diffusion equations (Equation to ): 12

\frac{\partial c}{\partial t} = D \frac{\partial^{2} c}{\partial x^{2}}, - L < x < L

t = 0, - L < x < L, c = c_{0}

t > 0, x = \pm L, - D \frac{\partial c}{\partial x} = k_{m} (c - {italicKc}_{italicext})

…”

Section: Experiments and Methodsmentioning

confidence: 99%

Section: Quantitation Of Triacetin In Loaded Silicone Rubber Sheetsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of uniaxial tensile strain on the release of small molecules from silicone rubber

Du,

Mefford

2023

J of Applied Polymer Sci

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Effects of molecular interactions on the release of small molecules from silicone rubber

Du,

Mefford

2024

J of Applied Polymer Sci

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Silicone rubber is a good candidate as a carrier of small molecules in such applications as drug, fragrance and semiochemical delivery. When one matrix is loaded, the molecular interactions between the molecules and the matrix may affect their release rates. For this reason, it is important to investigate the effects of molecular interactions on release to better develop delivery systems with desirable release rates. In this study, the mass transfer and diffusion coefficients of three model molecules (i.e., octanol, octyl acetate, and octyl butyrate) were determined by monitoring their release from silicone rubber sheets loaded using headspace gas chromatography–mass spectrometry. Differential scanning calorimetry was used to characterize the plasticizing effects and Fourier transform infrared spectroscopy was used to characterize the molecular interactions. It was found that the release of octanol conformed to the Fickian diffusion pattern at 1 wt% initial concentration but deviated as the concentration increased due to hydrogen bonding between octanol and the silanol group of the silica filler. When two small molecules were released simultaneously, the effects of one molecule on the diffusion coefficient of the other differed, a result explained by the competing effects of plasticizing and hydrogen bonding.

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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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Transport of Small Molecules in Loaded Natural Rubber: Experimental Measurement and Numerical Simulation

Cited by 4 publications

References 63 publications

Effects of uniaxial tensile strain on the release of small molecules from silicone rubber

Effects of uniaxial tensile strain on the release of small molecules from silicone rubber

Effects of molecular interactions on the release of small molecules from silicone rubber

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

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