TY - JOUR
T1 - Equilibrium swelling of multi-stimuli-responsive copolymer gels
AU - Drozdov, Aleksey D.
AU - Christiansen, Jesper de Claville
PY - 2021/9
Y1 - 2021/9
N2 - Copolymer gels prepared by polymerization of thermo-responsive and anionic monomers demonstrate strong sensitivity to several triggers such as temperature, pH and ionic strength of aqueous solutions. For biomedical applications of these materials (as on–off switches in controlled drug delivery and release), fine tuning of their volume phase transition temperature (VPTT) and a sharp decay in degree of swelling upon transition from the swollen to the collapsed state are needed. These requirements are fulfilled under swelling of copolymer gels and microgels in water under acidic conditions, but are violated when tests are conducted under alkaline conditions or in aqueous solutions of salts with physiological salinity. A model is developed for equilibrium swelling of multi-stimuli-responsive copolymer gels in aqueous solutions with arbitrary pH and molar fractions of a monovalent salt. Unlike conventional approaches, the model accounts for secondary interactions between chains (hydrogen bonding) to describe the kinetics of aggregation of hydrophobic segments above VPTT. Material constants are determined by fitting experimental swelling diagrams on poly(N-isopropylacrylamide–co–sodium acrylate) gels with various molar fractions of ionic monomers. The effects of temperature, pH and molar fraction of salt on the equilibrium degree of swelling below and above VPTT are studied numerically.
AB - Copolymer gels prepared by polymerization of thermo-responsive and anionic monomers demonstrate strong sensitivity to several triggers such as temperature, pH and ionic strength of aqueous solutions. For biomedical applications of these materials (as on–off switches in controlled drug delivery and release), fine tuning of their volume phase transition temperature (VPTT) and a sharp decay in degree of swelling upon transition from the swollen to the collapsed state are needed. These requirements are fulfilled under swelling of copolymer gels and microgels in water under acidic conditions, but are violated when tests are conducted under alkaline conditions or in aqueous solutions of salts with physiological salinity. A model is developed for equilibrium swelling of multi-stimuli-responsive copolymer gels in aqueous solutions with arbitrary pH and molar fractions of a monovalent salt. Unlike conventional approaches, the model accounts for secondary interactions between chains (hydrogen bonding) to describe the kinetics of aggregation of hydrophobic segments above VPTT. Material constants are determined by fitting experimental swelling diagrams on poly(N-isopropylacrylamide–co–sodium acrylate) gels with various molar fractions of ionic monomers. The effects of temperature, pH and molar fraction of salt on the equilibrium degree of swelling below and above VPTT are studied numerically.
KW - Copolymer gel
KW - Equilibrium swelling
KW - Multi-stimuli-responsive gel
KW - Volume phase transition temperature
UR - http://www.scopus.com/inward/record.url?scp=85108150073&partnerID=8YFLogxK
U2 - 10.1016/j.jmbbm.2021.104623
DO - 10.1016/j.jmbbm.2021.104623
M3 - Journal article
SN - 1751-6161
VL - 121
JO - Journal of the Mechanical Behavior of Biomedical Materials
JF - Journal of the Mechanical Behavior of Biomedical Materials
M1 - 104623
ER -