title: Influence of substitution pattern on solution behavior of hydroxypropyl methylcellulose.
abstract: Industrially produced hydroxypropyl methylcellulose (HPMC) is a chemically heterogeneous material, and it is thus difficult to predict parameters related to function on the basis of the polymer's average chemical values. In this study, the solution behavior of seven HPMC batches was correlated to the molecular weight, degree of substitution, and substituent pattern. The initial onset of phase separation, so-called clouding, generally followed an increased average molecular weight and degree of substitution. However, the slope of the clouding curve was affected by the substitution pattern, where the heterogeneously substituted batches had very shallow slopes. Further investigations showed that the appearance of a shallow slope of the clouding curve was a result of the formation of reversible polymer structures, formed as a result of the heterogeneous substituent pattern. These structures grew in size with temperature and concentration and resulted in an increase in the viscosity of the solutions at higher temperatures.
authors.affiliation: Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden. annlov@chalmers.se
authors.forename: Anna
authors.initials: A
authors.lastname: Viridén
authors.forename: Bengt
authors.initials: B
authors.lastname: Wittgren
authors.forename: Thomas
authors.initials: T
authors.lastname: Andersson
authors.forename: Susanna
authors.initials: S
authors.lastname: Abrahmsén-Alami
authors.forename: Anette
authors.initials: A
authors.lastname: Larsson
mesh_terms: D065347:Hypromellose Derivatives; D008747:Methylcellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D008970:Molecular Weight; D010316:Particle Size; D012996:Solutions; D013499:Surface Properties; D013696:Temperature; D014783:Viscosity
chemical_list: D012996:Solutions; D065347:Hypromellose Derivatives; D008747:Methylcellulose