title: The importance of the molecular weight of ethyl cellulose on the properties of aqueous-based controlled release coatings.
abstract: Previous investigations of aqueous based ethyl cellulose (EC) latex dispersions have mainly focused on the commercially available viscosity grade 20cps. In this study, dispersions of EC with varying viscosity grades (which correspond to molecular weights), ranging from 4 to 100 cps, were produced and characterised. The dispersions showed particle sizes around 200nm and highly negative ζ-potentials (approx. -100mV), which indicated stable dispersions as confirmed by sedimentation studies. The different latexes were used to produce free-standing film coatings. We hypothesised that the different viscosity grades of EC would result in different properties of the films. We found that an increase in viscosity grade (and higher molecular weight) resulted in lower coalescence between the particles during film formation and thus to higher water permeability than in film coatings of lower molecular weight. After exposure to water the EC 4cps and 20cps film coatings had a more porous structure in the side facing the air during production and drying after immersion in water. Molecular weight is therefore a factor that should be considered when producing pharmaceutical coatings for controlled release.
authors.affiliation: Pharmaceutical Technology, Applied Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden; SuMo Biomaterials, VINN Excellence Center, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
authors.forename: Jurgita
authors.initials: J
authors.lastname: Kazlauske
authors.affiliation: SuMo Biomaterials, VINN Excellence Center, Chalmers University of Technology, 412 96 Gothenburg, Sweden; Theoretical Chemistry, Lund University, P.O. Box 124, 221 00 Lund, Sweden.
authors.forename: Sofie
authors.initials: S
authors.lastname: Gårdebjer
authors.affiliation: Pharmaceutical Technology, Applied Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
authors.forename: Sara
authors.initials: S
authors.lastname: Almer
authors.affiliation: Pharmaceutical Technology, Applied Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden; SuMo Biomaterials, VINN Excellence Center, Chalmers University of Technology, 412 96 Gothenburg, Sweden. Electronic address: anette.larsson@chalmers.se.
authors.forename: Anette
authors.initials: A
authors.lastname: Larsson
mesh_terms: D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D003692:Delayed-Action Preparations / Q000737:chemistry*; D007840:Latex / Q000737:chemistry; D008970:Molecular Weight; D010316:Particle Size; D010539:Permeability; D016062:Porosity; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D003692:Delayed-Action Preparations; D007840:Latex; D014867:Water; C013517:ethyl cellulose; D002482:Cellulose
keywords: Coalescence; Ethylcellulose; Film coatings; Latex; Water permeability