Synergistic Temperature and pH Effects on Glass (T_g) and Stimuli-Responsive (T_SR) Transitions In Poly(N-Acryloyl-N'-Propylpiperazine-co-2-Ethoxyethyl Methacrylate) Copolymers

Authors

Marek W. Urban, University of Southern MississippiFollow
Fang Liu, University of Southern MississippiFollow
William L. Jarrett, University of Southern MississippiFollow

Document Type

Article

Publication Date

2011

School

Polymer Science and Engineering

Abstract

N-Acryloyl-N′-propylpiperazine (AcrNPP) and 2-ethoxyethyl methacrylate (EEMA) monomers were copolymerized to form random stimuli-responsive p(AcrNPP/EEMA) copolymers in a form of colloidal dispersions which upon coalesce form uniform films. The presence of AcrNPP units facilitates temperature and pH responsiveness, thus resulting in composition-dependent and pH–temperature sensitive endothermic transitions: the glass (T_g) and stimuli-responsive (T_SR) transitions. These studies show that the relationship between the newly discovered T_SR and known T_g relaxations can be predicted by the following formula: 1/T_SR = [T_g1 × T_g2 × (T_binary − T)]/[T_binary × T × (T_g1 − T_g2) × T_g] + (T_g1 × T − T_binary × T_g2)/[T_binary × T × (T_g1 − T_g2)], where T_SR is the stimuli-responsive transition temperature, T_g is the glass transition temperature of the copolymer; T_binary is the temperature of stimuli-responsive homopolymer in a binary polymer–water equilibrium, T_g1 and T_g2 are the glass transition temperatures of stimuli-responsive and non-stimuli-responsive homopolymers, respectively, and T is the film formation temperature. Experimental spectroscopic and differential scanning calorimetry (DSC) evidence showed that dipole–dipole interactions are responsible for the molecular changes at the T_SR for a non-protonated state, and the shift of the T_SR under protonated conditions is attributed to the synergistic pH and temperature effects associated with H-bonding and conformational backbone and side chain rearrangements. Computer simulations also showed that the buckling of the copolymer backbone and collapse of propylpiperazine groups occur above T_SR. The total energies (ΔE_total) of the T_SR transitions for protonated and non-protonated states are 159 and 132 kcal mol⁻¹, respectively, and are in good agreement with the energy values determined experimentally (DSC).

Comments

Originally published in Polymer Chemistry, 2011, 2, 963-969

Full-text available for USM authenticated users

Publication Title

Polymer Chemistry

Volume

2

Issue

4

First Page

963

Last Page

969

Recommended Citation

Urban, M. W., Liu, F., Jarrett, W. L. (2011). Synergistic Temperature and pH Effects on Glass (T_g) and Stimuli-Responsive (T_SR) Transitions In Poly(N-Acryloyl-N'-Propylpiperazine-co-2-Ethoxyethyl Methacrylate) Copolymers. Polymer Chemistry, 2(4), 963-969.
Available at: https://aquila.usm.edu/fac_pubs/28