Skip to Content
Merck
  • Effects of molecular weight on permeability and microstructure of mixed ethyl-hydroxypropyl-cellulose films.

Effects of molecular weight on permeability and microstructure of mixed ethyl-hydroxypropyl-cellulose films.

European journal of pharmaceutical sciences : official journal of the European Federation for Pharmaceutical Sciences (2012-11-20)
Helene Andersson, Johan Hjärtstam, Mats Stading, Christian von Corswant, Anette Larsson
ABSTRACT

Films of ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC) can be used for extended release coatings in oral formulations. The permeability and microstructure of free EC/HPC films with 30% w/w HPC were studied to investigate effects of EC molecular weight. Phase separation during film spraying and subsequent HPC leaching after immersion in aqueous media cause pore formation in such films. It was found that sprayed films were porous throughout the bulk of the films after water immersion. The molecular weight affected HPC leaching, pore morphology and film permeability; increasing the molecular weight resulted in decreasing permeability. A model to distinguish the major factors contributing to diffusion retardation in porous films showed that the trend in permeability was determined predominantly by factors associated with the geometry and arrangement of pores, independent of the diffusing species. The film with the highest molecular weight did, however, show an additional contribution from pore wall/permeant interactions. In addition, rapid drying and increasing molecular weight resulted in smaller pores, which suggest that phase separation kinetics affects the final microstructure of EC/HPC films. Thus, the molecular weight influences the microstructural features of pores, which are crucial for mass transport in EC/HPC films.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Hydroxypropyl cellulose, average Mw ~80,000, average Mn ~10,000, powder, 20 mesh particle size (99% through)
Sigma-Aldrich
Hydroxypropyl cellulose, average Mw ~370,000, powder, 20 mesh particle size (99% through)
Sigma-Aldrich
Hydroxypropyl cellulose, average Mw ~1,000,000, powder, 20 mesh particle size (99% through)
Sigma-Aldrich
Hydroxypropyl cellulose, average Mw ~100,000, powder, 20 mesh particle size (99% through)
Sigma-Aldrich
Ethyl cellulose, viscosity 46 cP, 5 % in toluene/ethanol 80:20(lit.), extent of labeling: 48% ethoxyl
Sigma-Aldrich
Ethyl cellulose, viscosity 10 cP, 5 % in toluene/ethanol 80:20(lit.), extent of labeling: 48% ethoxyl
Sigma-Aldrich
Ethyl cellulose, viscosity 22 cP, 5 % in toluene/ethanol 80:20(lit.), extent of labeling: 48% ethoxyl
Sigma-Aldrich
Ethyl cellulose, viscosity 300 cP, 5 % in toluene/ethanol 80:20(lit.), extent of labeling: 48% ethoxyl
Sigma-Aldrich
Ethyl cellulose, viscosity 100 cP, 5 % in toluene/ethanol 80:20(lit.), extent of labeling: 48% ethoxyl
Sigma-Aldrich
Ethyl cellulose, 48.0-49.5% (w/w) ethoxyl basis
Sigma-Aldrich
Ethyl cellulose, viscosity 4 cP, 5 % in toluene/ethanol 80:20(lit.), extent of labeling: 48% ethoxyl
Sigma-Aldrich
Ethyl cellulose, CP, viscosity 45 cP 
Sigma-Aldrich
Ethyl cellulose, 48.0-49.5% (w/w) ethoxyl basis