Poly(DEAEMa-co-PEGMa):  A New pH-Responsive Comb Copolymer Stabilizer for Emulsions and Dispersions

Abstract

Stimulus responsive copolymers are an important class of surfactants that are attracting growing attention in the literature. When used to stabilize colloids, they confer responsiveness to an otherwise nonresponsive system. In this work, a new pH-responsive comb copolymer surfactant, poly(DEAEMa-co-PEGMa), where DEAEMa and PEGMa are diethylaminoethyl methacrylate and poly(ethylene glycol) methacrylate, is introduced and used to stabilize emulsions and particulate dispersions. The copolymer contained 70 mol % of DEAEMa. Turbidity versus pH measurements and photon correlation spectroscopy of the copolymer solutions revealed pH-triggered collapse of the chains above the pK(a). The surface activity of the copolymer increased with pH. The minimum surface tension measured was 33.6 mN/m at pH = 10. These data enabled identification of the pK(a) for poly(DEAEMa-co-PEGMa) as 6.8. The emulsions consisted of tetradecane-in-water and had a droplet size in the range 5-11 mum. They were slightly flocculated when the pH value was close to the isoelectric point. The emulsions phase separated at low pH values. The particulate dispersions were based on carbendazim, which is a fungacide, and had an average size of 1.8 mum. The data for the emulsions and carbendazim dispersions show that the extent of flocculation decreases with decreasing size of the dispersed phase. Analysis of the data suggest that optimum emulsion stability occurs in the pH region of 5.3-6.8 as judged by turbidity measurements. Electrophoretic mobility measurements as a function of pH for the emulsions and carbendazim dispersions reveal a similar isoelectric point in the range of 8.5-9.0, which is about two pH units higher than the pK(a) of the copolymer. A mechanism that explains the pH-responsive stability of the emulsions and dispersions is presented and discussed.

Preparation of pH‐Responsive Polymer Core–Shell Nanospheres for Delivery of Hydrophobic Antineoplastic Drug Ellipticine

“…It is well known that poly(DEAEMA) is a pH‐responsive biocompatible polymer and a weak acid with a p K a of about 7.3 . The DEAEMA macromolecules can progressively change their conformation structure with a variation of pH from a hydrophilic state at low pH to a hydrophobic state at high pH because of the deprotonation of charged groups in the DEAEMA macromolecules at high pH values . DEAEMA has been used by many researchers to prepare pH‐responsive particulate systems, and it was incorporated into the objective nanospheres in this research to induce the pH‐responsive characteristic.…”

“…On the one hand, ellipticine molecules diffused through the polymer mother matrix via a leakage process and the diffusion of ellipticine present in the “donor” solution was in equilibrium with the dissociation between ellipticine and the polymer matrix. DEAEMA macromolecules are known to have a pH‐responsive property due to the proton‐transfer equilibrium induced by the amino groups of the core DEAEMA macromolecules . Increasing [H + ] strength in the solution will lead to progressively more protonated poly(DEAEMA) segment (increase of the average charge per polymer chain), and thus the hydrophilicity of the polymer chains.…”

Micellization of a di‐block copolymer in ethylene glycol and its utilization for suspension of carbonaceous nanostructures

“…The combination of the PEGMA block (highly soluble in EG) and the relatively long “solvophobic” tail (the DEAEMA‐ co ‐BMA residue) was expected to favor micellization in EG. This polymer is known to assemble into spherical micelles in aqueous solutions with a low CMC, that depends on the pH of the solutions, as the DEAEMA is a weak (cationic) polybase with a p K a of the conjugated acid of 7.4 …”

Synthesis and self-assembly behavior of pH-responsive star-shaped POSS-(PCL-P(DMAEMA-co-PEGMA))16 inorganic/organic hybrid block copolymer for the controlled intracellular delivery of doxorubicin

“…15,16 Moreover, inorganic/organic hybrid polymers have attracted a great deal of research interest, a particularly noticeable example is organic/inorganic hybrid polymers based on polyhedral oligomeric silsesquioxane (POSS). As a U.S. Food and drug administration approved biomedical polymer, biodegradable poly(ε-caprolactone) (PCL) and PCL-based biomaterials have been increasingly investigated for pharmaceutical and biomedical applications, 7,24 and micelles formed from block copolymers consisting of poly(εcaprolactone) (PCL) and poly(ethylene glycol)methyl ether methacrylate (PEGMA) have drawn considerable interest, the PEGMA with excellent biocompatibility forms the hydrophilic corona in the micelles, 25,26 and in the past years, Poly(2-(N, Ndimethylamino)ethyl methacrylate) (PDMAEMA) is a weak base with a pKa at about 7. Plenty of star-shaped polycations, POSS is containing a biocompatible core and display excellent performance in gene therapy.…”