Structure formation and coarsening kinetics of phase-separated spin-coated ethylcellulose/hydroxypropylcellulose films
Artikel i vetenskaplig tidskrift, 2022

Porous phase-separated ethylcellulose/hydroxypropylcellulose (EC/HPC) films are used to control drug transport from pharmaceutical pellets. The drug transport rate is determined by the structure of the porous films that are formed as water-soluble HPC leaches out. However, a detailed understanding of the evolution of the phase-separated structure in the films is lacking. In this work, we have investigated EC/HPC films produced by spin-coating, mimicking the industrial fluidized bed spraying. The aim was to investigate film structure evolution and coarsening kinetics during solvent evaporation. The structure evolution was characterized using confocal laser scanning microscopy and image analysis. The effect of the EC:HPC ratio (15 to 85 wt% HPC) on the structure evolution was determined. Bicontinuous structures were found for 30 to 40 wt% HPC. The growth of the characteristic length scale followed a power law, L(t) ∼ t(n), with n ∼ 1 for bicontinuous structures, and n ∼ 0.45-0.75 for discontinuous structures. The characteristic length scale after kinetic trapping ranged between 3.0 and 6.0 μm for bicontinuous and between 0.6 and 1.6 μm for discontinuous structures. Two main coarsening mechanisms could be identified: interfacial tension-driven hydrodynamic growth for bicontinuous structures and diffusion-driven coalescence for discontinuous structures. The 2D in-plane interface curvature analysis showed that the mean curvature decreased as a function of time for bicontinuous structures, confirming that interfacial tension is driving the growth. The findings of this work provide a good understanding of the mechanisms responsible for morphology development and open for further tailoring of thin EC/HPC film structures for controlled drug release.


Pierre Carmona

Chalmers, Fysik, Nano- och biofysik

RISE Research Institutes of Sweden

Magnus Röding

RISE Research Institutes of Sweden

Chalmers, Matematiska vetenskaper, Tillämpad matematik och statistik

Aila Särkkä

Chalmers, Matematiska vetenskaper, Tillämpad matematik och statistik

Christian von Corswant

AstraZeneca AB

Eva Olsson

Chalmers, Fysik, Nano- och biofysik

Niklas Lorén

RISE Research Institutes of Sweden

Chalmers, Fysik, Nano- och biofysik

Soft Matter

1744-683X (ISSN) 1744-6848 (eISSN)

Vol. 18 16 3206-3217

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Vetenskapsrådet (VR) (2018-03986), 2019-01-01 -- 2022-12-31.


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