title: The influence of the molecular weight of the water-soluble polymer on phase-separated films for controlled release.
abstract: Hydroxypropyl cellulose (HPC) and ethyl cellulose (EC) can be used for extended release coatings, where the water-soluble HPC may act as a pore former. The aim was to investigate the effect of the molecular weight of HPC on the microstructure and mass transport in phase-separated freestanding EC/HPC films with 30% w/w HPC. Four different HPC grades were used, with weight averaged molecular weights (Mw) of 30.0 (SSL), 55.0 (SL), 83.5 (L) and 365 (M) kg/mol. Results showed that the phase-separated structure changed from HPC-discontinuous to bicontinuous with increasing Mw of HPC. The film with the lowest Mw HPC (SSL) had unconnected oval-shaped HPC-rich domains, leaked almost no HPC and had the lowest water permeability. The remaining higher Mw films had connected complex-shaped pores, which resulted in higher permeabilities. The highest Mw film (M) had the smallest pores and very slow HPC leakage, which led to a slow increase in permeability. Films with grade L and SL released most of their HPC, yet the permeability of the L film was three times higher due to greater pore connectivity. It was concluded that the phase-separated microstructure, the level of pore percolation and the leakage rate of HPC will be affected by the choice of HPC Mw grade used in the film and this will in turn have strong impact on the film permeability.
authors.affiliation: SP Food and Bioscience, Structure and Material Design, PO BOX 5301, SE-402 29 Gothenburg, Sweden; Chalmers University of Technology, Department of Material and Manufacturing Technology, SE-412 96 Gothenburg, Sweden; SuMo BIOMATERIALS, VINN Excellent Centre, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden. Electronic address: helene.mi.andersson@gmail.com.
authors.forename: Helene
authors.initials: H
authors.lastname: Andersson
authors.affiliation: SuMo BIOMATERIALS, VINN Excellent Centre, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden; Chalmers University of Technology, Department of Mathematical Statistics, SE-412 96 Gothenburg, Sweden.
authors.forename: Henrike
authors.initials: H
authors.lastname: Häbel
authors.affiliation: SuMo BIOMATERIALS, VINN Excellent Centre, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden; Chalmers University of Technology, Department of Physics, SE-412 96 Gothenburg, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Olsson
authors.affiliation: SP Food and Bioscience, Structure and Material Design, PO BOX 5301, SE-402 29 Gothenburg, Sweden; Chalmers University of Technology, Department of Chemistry and Chemical Engineering, SE-412 96 Gothenburg, Sweden.
authors.forename: Sofie
authors.initials: S
authors.lastname: Sandhagen
authors.affiliation: AstraZeneca R&D Mölndal, SE-431 83 Mölndal, Sweden.
authors.forename: Christian
authors.initials: C
authors.lastname: von Corswant
authors.affiliation: AstraZeneca R&D Mölndal, SE-431 83 Mölndal, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Hjärtstam
authors.affiliation: Chalmers University of Technology, Department of Chemistry and Chemical Engineering, SE-412 96 Gothenburg, Sweden; Akzo Nobel Pulp and Performance Chemicals AB, 445 80 Bohus, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Persson
authors.affiliation: SP Food and Bioscience, Structure and Material Design, PO BOX 5301, SE-402 29 Gothenburg, Sweden; Chalmers University of Technology, Department of Material and Manufacturing Technology, SE-412 96 Gothenburg, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Stading
authors.affiliation: SuMo BIOMATERIALS, VINN Excellent Centre, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden; Chalmers University of Technology, Department of Chemistry and Chemical Engineering, SE-412 96 Gothenburg, Sweden.
authors.forename: Anette
authors.initials: A
authors.lastname: Larsson
mesh_terms: D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry / Q000493:pharmacokinetics; D003692:Delayed-Action Preparations / Q000737:chemistry / Q000493:pharmacokinetics; D065546:Drug Liberation; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry* / Q000493:pharmacokinetics; D014867:Water / Q000737:chemistry* / Q000378:metabolism
chemical_list: D003692:Delayed-Action Preparations; D011108:Polymers; D014867:Water; C013517:ethyl cellulose; D002482:Cellulose; C008079:hydroxypropylcellulose
keywords: Controlled release; Ethyl cellulose; Film coating; Hydroxypropyl cellulose; Molecular weight; Pellet formulation; Phase separation