Doubly thermo-responsive brush-linear diblock copolymers and formation of core-shell-corona micelles

An Advanced Material with Synergistic Viscoelasticity Enhancement of Hydrophobically Associated Water-Soluble Polymer and Surfactant

In order to prepare materials with controllable properties, changeable microstructure, and high viscoelasticity solution with low polymer and surfactant concentration, a composite is constituted by adding surfactant (sodium dodecyl sulfate, SDS) to hydrophobically associated water-soluble polymer (abbreviated as PAAC) solution. The viscoelasticity, aggregate microstructure, and interaction mechanism of the composite are investigated by rheometery, Cryo-transmission electron microscopy (Cryo-TEM), and fluorescence spectrum. The results show that when the mass ratio of polymer to surfactant is 15:1, the viscosity of the composite reaches the maximum. The viscosity of the composite system increases hundredfold. The viscosity plateau under dynamic shear is generated. The composite has the properties of high viscoelasticity, strong shear thinning behavior, and good salt tolerance, and temperature resistance. The maximum viscosity of the composite is shown at the salinity of 20000 mg L^-1 . In addition, there is no phase separation in the composite with the increase of polymer and surfactant concentration, which indicates the good stability of the system. It is proposed a method to obtain a high viscoelasticity solution by adding surfactants without wormlike micelles to a hydrophobically associated water-soluble polymer solution.

Thermoresponsive Gels

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.

Recent Advances in Dual Temperature Responsive Block Copolymers and Their Potential as Biomedical Applications

The development of stimuli responsive polymers has progressed significantly with novel preparation techniques, which has allowed access to new materials with unique properties. Dual thermoresponsive (double temperature responsive) block copolymers are particularly of interest as their properties can change depending on the lower critical solution temperature (LCST) or upper critical solution temperature (UCST) of each segment. For instance, these block copolymers can change from being hydrophilic, to amphiphilic or to hydrophobic simply by changing the solution temperature without any additional chemicals and the block copolymers can change from being fully solubilized to self-assembled structures to macroscopic aggregation/precipitation. Based on the unique solution properties, these dual thermo-responsive block copolymers are expected to be suitable for biomedical applications. This review is divided into three parts; LCST-LCST types of block copolymers, UCST-LCST types of block copolymers, and their potential as biomedical applications.

pH-modulated double LCST behaviors with diverse aggregation processes of random-copolymer grafted silica nanoparticles in aqueous solution

Thermo-responsive hybrid nanoparticles composed of silica-core and poly(N,N-dimethylaminoethyl methacrylate-co-N-isopropylacrylamide) P(DMAEMA-co-NIPAM) copolymer-shell were prepared through a one-pot ATRP technique.

Doubly thermo-responsive nanoparticles constructed with two diblock copolymers prepared through the two macro-RAFT agents co-mediated dispersion RAFT polymerization

Doubly thermo-responsive nanoparticles constructed with two diblock copolymers were prepared, and the nanoparticles exhibit a two-step phase-transition with increasing temperature.