Thermoresponsive Gels

Abstract

Thermoresponsive gelling materials constructed from natural and synthetic polymers can be used to provide triggered action and therefore customised products such as drug delivery and regenerative medicine types as well as for other industries. Some materials give Arrhenius-type viscosity changes based on coil to globule transitions. Others produce more counterintuitive responses to temperature change because of agglomeration induced by enthalpic or entropic drivers. Extensive covalent crosslinking superimposes complexity of response and the upper and lower critical solution temperatures can translate to critical volume temperatures for these swellable but insoluble gels. Their structure and volume response confer advantages for actuation though they lack robustness. Dynamic covalent bonding has created an intermediate category where shape moulding and self-healing variants are useful for several platforms. Developing synthesis methodology-for example, Reversible Addition Fragmentation chain Transfer (RAFT) and Atomic Transfer Radical Polymerisation (ATRP)-provides an almost infinite range of materials that can be used for many of these gelling systems. For those that self-assemble into micelle systems that can gel, the upper and lower critical solution temperatures (UCST and LCST) are analogous to those for simpler dispersible polymers. However, the tuned hydrophobic-hydrophilic balance plus the introduction of additional pH-sensitivity and, for instance, thermochromic response, open the potential for coupled mechanisms to create complex drug targeting effects at the cellular level.

Fine‐tuning of phase behavior of oxazoline copolymer‐based organic–inorganic hybrids as solid‐supported sol–gel materials

“…The peak at 950 cm −1 is observed due to Si OH stretch. A small absorption at 760 cm −1 is attributable to the incomplete hydrolysis of TMOS backbone of Si OCH 3,26,32 leading to a development of both 3D network of the hybrid with some terminal OH (Scheme 2). A weak broad band was observed from 3600 to 3000 cm −1 which is ascribed to the Si O H stretch formed during the hydrolysis of the methoxy groups of TMOS.…”

“…[1][2][3] Of which, thermo-sensitive polymers are of great significant due to ease to control transition temperature manually and naturally as well. [1][2][3] Of which, thermo-sensitive polymers are of great significant due to ease to control transition temperature manually and naturally as well.…”

“…Stimuli-responsive "smart" polymers are being researched intensively since many years ago as these are capable of showing distinct changes in acknowledgement to external stimuli such as light, heat, pH, electric, or magnetic fields. [1][2][3] Of which, thermo-sensitive polymers are of great significant due to ease to control transition temperature manually and naturally as well. These polymers tend to undergo coil-to-globule phase change under the influence of temperature, 4 thereby showcase phase change phenomenon like as lower critical solution temperature (LCST) and upper critical solution temperature (UCST) depending upon their miscibility, optical, and other physiochemical properties.…”

Progress in the Field of Water‐ and/or Temperature‐Triggered Polymer Actuators

“…These gels, which are called responsive gels, provide means of controlling fast actuation (on‐off) by external triggers. The gels triggered by temperature and pH are called thermo‐ and pH‐responsive gels, respectively …”

Preparation and Application in Drug Storage and Delivery of Agarose Nanoparticles

“…It is well known that agarose presents a sol-gel transition around human physiological temperature (37°C). The sol-gel transition is strongly dependent on the length of agarose chains and the cross-linking degree of the polymer network [32,40] Thus, it is expected that the increase of the temperature beyond the transition temperature can lead to a significant change of the nanoparticles size which can be an advantage for applications in which the load and release of active compounds from the gel matrix are required. However, most important than the gel swelling upon the increase of the temperature is the reversibility of such process, i.e., the reversible swelling-shrinking of the gel as result of its subsequent heating and cooling.…”