Well-Defined Thermoresponsive Copolymers with Tunable LCST and UCST in Water

Abstract

A thermoresponsive polymer, poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), was successfully synthesized by atom transfer radical polymerization (ATRP). Different amounts of 1,3-propanesultone were used as quaternization agent to transit the PDMAEMA into partially modified poly(zwitterions), resulting in p[DMAEMA-co-3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate] (PDMAEMA-co-PDMAPS). Molecular weight, molecular weight distribution, and degree of quarternization were determined by gel permeation chromatography (GPC) and 1 H NMR spectroscopy. The transmission spectra of the 1.0 wt % aqueous solutions of the resulting polymers at 650 nm were measured as a function of temperature. Results showed that the lower critical solution temperature (LCST) and the upper critical solution temperature (UCST) could be easily controlled by the different composition of dimethylamino and zwitterion groups. The effect of partial quaternization on thermoresponsive properties was also studied by dynamic light scattering (DLS) with the same aqueous concentration (1.0 wt %) as employed for turbidimetry studies. The LCST and UCST values measured by DLS correlated well with those determined by turbidimetry.

Stimuli‐responsive amphiphilic PDMAEMA‐b‐PLMA copolymers and their cationic and zwitterionic analogs

“…A decrease of intensity and an increase of R h is observed with increasing temperature. It is known that PDMAEMA is thermoresponsive in water solutions, having an LCST in the range 40–50 °C …”

“…When subjected to changes in pH and/or temperature it can switch from a hydrophilic to a less hydrophilic character. Also, PDMAEMA presents a lower critical solution temperature (LCST) in water in the range 40–50 °C, making it an attractive target for both physical studies and biomedical applications. In addition, due to its intrinsic cationic charge PDMAEMA has been proven to be an efficient gene‐transfer agent due to its ability in binding DNA by electrostatic interactions .…”

Tuning the Phase Transition from UCST‐Type to LCST‐Type by Composition Variation of Polymethacrylamide Polymers

“…Thermoresponsive polymers showing lower critical solution or upper critical solution temperatures (LCST and UCST, respectively) in water as well as in electrolyte solutions are of great interest in a wide field of applications . In the last more than two decades, a lot of research efforts were devoted toward finding out new examples of polymers exhibiting LCST‐type transition, tuning of their critical temperatures, understanding the mechanism of phase transitions and applications .…”

Effect of the Degree of Quaternization and Molar Mass on the Cloud Point of Poly[2‐(dimethylamino)ethyl methacrylate] Aqueous Solutions: A Systematic Investigation

“…Above the respective LCST, the polymer chains undergo a phase separation from the aqueous solution as a consequence of the rupture of the hydrogen bonds and increasing hydrophobic polymer–polymer interactions, showing a cloud point during turbidity measurements of polymer aqueous solutions. In this regard, poly[2‐(dimethylamino)ethyl methacrylate] p(DMAEMA) represents an interesting water soluble polymer that has been proposed for different biological applications and is one of the most investigated polymers whose aqueous solutions exhibit a cloud point behavior as a function of different properties such as molar mass, pH value, or comonomer composition . Despite many literature reports on this subject, and to the best of our knowledge, a systematic investigation is lacking describing the relationship of the cloud point of p(DMAEMA) with the molar mass in combination with a gradual change in its hydrophilic nature, i.e., by the quaternization degree of the tertiary amine present in its structure, still needs to be addressed.…”

“…In this regard, Armes and co‐workers demonstrated that a partial quaternization of a p(DMAEMA) homopolymer with a number average molar mass ( M n ) of 5300 g mol −1 , increased significantly the cloud points (1.0% w/v aqueous solutions at pH 8.8). More recently, Jung and Lee have reported that the cloud point of p(DMAEMA) ( M n = 15 700 g mol −1 ) can be adjusted at certain extent by quaternizing the polymer at different degrees by means of a rather demanding reaction with 1,3‐propane sulfone units. These latter investigations were based on the utilization of single p(DMAEMA)s with a predefined M n and, therefore, the effect of the molar mass on the cloud point was not addressed.…”