A New Thermo-, pH-, and CO₂-Responsive Homopolymer of Poly[N-[2-(diethylamino)ethyl]acrylamide]: Is the Diethylamino Group Underestimated?

Abstract

A new multi-stimuli-responsive homopolymer of poly [N-[2-(diethylamino)ethyl]acrylamide] (PDEAEAM), which combines the thermoresponsive and pH/CO 2 -responsive moieties of the diethylamino and acrylamide groups, was proposed and synthesized by RAFT polymerization. Well-defined PDEAEAM was synthesized by solution RAFT polymerization as indicated by the linear increase in the polymer molecular weight with the monomer conversion and the narrow molecular weight distribution. The appending diethylamino group in the polymer backbone was found to be crucial to determine the thermoresponse of PDEAEAM in water. The parameters including the polymerization degree, the polymer concentration, the deuterated solvent, the terminal attached on the polymer backbone, the additives of salt and urea, and pH and bubbling CO 2 affecting the thermoresponse of PDEAEAM in aqueous solution at the lower critical solution temperature (LCST) were investigated. The temperature-variable 1 H NMR analysis suggests that the dehydration of PDEAEAM at temperature above LCST is ascribed to the weakened hydrogen bonding between the CONHCH 2 and/or (CH 2 N(CH 2 CH 3 ) 2 ) moieties with the solvent of water. The proposed multi-stimuli-responsive homopolymer of PDEAEAM has two advantages of (1) the convenient and controllable RAFT synthesis and (2) the pH/CO 2 tunable LCST at ∼36 °C being very close to body temperature.

The influence of pH, hydrolysis and degree of substitution on the temperature‐sensitive properties of polyaspartamides

“…Transmittance was measured at different temperatures and samples were equilibrated for 4 min before each measurement. The LCST of the polymer was defined as the temperature corresponding to a 50% reduction in the transmittance of the solution at 20 °C . The LCST of the PSI‐TS and PAA‐TS samples was determined on varying the pH between 3.2 and 3.8.…”

The Dependence of the Cloud Point, Clearing Point, and Hysteresis of Poly(N-isopropylacrylamide) on Experimental Conditions: The Need for Standardization of Thermoresponsive Transition Determinations

“…However, in cases when the transmittance does not reach 50%, this is meaningless, or when the transmittance does not change between 100 and 0% and/or when an asymmetric curve is obtained, serious uncertainties may arise with the T CP (50%) values as a reliable choice for cloud point. In order to overcome this problem, there have been reports in which the transmittance–temperature or absorbance–temperature curves are normalized between 0 and 1 by selecting the minimal value as zero and the measured maximum value as 1, and the temperature value at 0.5 is selected as T CP (n50%) or the temperature at 1% change of the normalized absorbance is considered as the cloud point . However, significant distortion of the measured curves may occur with this normalization.…”

A new thermoresponsive polymer of poly(N-acryloylsarcosine methyl ester) with a tunable LCST

“…[1][2][3] Amongst the thermoresponsive polymers, an abundance of macromolecules exhibiting a lower critical solution temperature (LCST) with a coil-to-globule transition in water solution, are probably the most investigated. To date, the LCSTtype thermoresponsive polymers can be summarized into six categories: poly[oligo(ethylene glycol) (meth)acrylate]s, [5][6][7] poly(2alkyl-2-oxazoline)s, 8,9 poly(vinyl methyl ether)s, 10,11 polypeptides, [12][13][14] N-alkyl-substituted poly(aminoethyl methacrylate)s, [15][16][17][18] and especially N-substituted poly(meth)acrylamides with a pendant of amide group. Recently, many kinds of technologies have verified that the amide pendant of polyacrylamide plays key role in forming hydrogen bonding with water or the additives (e.g.…”