Fast, multi-responsive microgels based on photo-crosslinkable poly(2-(dimethylamino)ethyl methacrylate)

Poly(N,N-dimethylaminoethyl methacrylate) as a bioactive polyelectrolyte-production and properties

Poly(N,N-dimethylaminoethyl methacrylate) is a polyelectrolyte with many important chemical and physical properties and, above all, offers a wide range of interesting biological properties. Currently, research on this polymer is ongoing in several centres around the world. The process of polymerizing the monomer is not easy, as there are difficulties in obtaining a product with repeatable properties. This work collected and described most of the currently known and used polymerization methods of N,N-dimethylaminoethyl methacrylate, taking into account the type of method, the solvent used, the initiator, as well as the process temperature and the average molecular weight of the polymer obtained. The most important properties of the discussed polymer, such as solubility, bioactivity, hydrophilicity, cytotoxicity, conductivity, and thermal and hydrodynamic parameters, are discussed on the basis of the available scientific literature. This work aims, among other things, to increase the possibility of using poly(N,N-dimethylaminoethyl methacrylate) as a material in advanced practical applications. Therefore, various methods of applied use of the polymer in question have also been described so far. Copolymers of the N,N-dimethylaminoethyl methacrylate are now too large a collection to fit in a single publication. Therefore, only the most interesting examples were cited in this work.

Preparation of Hydroxypropylcellulose Membranes using Slow Ionotropic Reactions Configured in an Experimental Design

This study applied a Face-Centered Central Composite Design to prepare various hydroxypropylcellulose (HPC) membranes using slow ionotropic reactions. After the assessment of various salting-out agents, sodium carbonate was selected as the ideal electrolyte capable of inducing sufficient membrane growth. The factors studied included the concentration of hydroxypropylcellulose [HPC] (1-2%w/v), concentration of salt [Salt] (10-20%w/v) and the salting-out reaction time (SORT) (96-144 hours). The experimental and predicted responses in the design included the measurement of the Brinell Hardness Number (BHN), gel thickness, moisture absorption and membrane erosion. Surface morphological examination revealed that the membranes varied from highly porous to closely packed networks. Statistically, the experimental and predicated response values showed no significant differences (p 0.05) based on a one way ANOVA. A significant decrease in BHN was observed as the [HPC] was increased. This was attributed to an increase in the elasticity of the membrane. The increase in moisture absorption was accompanied by an increase in gel thickness and subsequently an increase in membrane erosion around the peripheral areas of the gel structure. In the case of the [Salt], all response values were reduced above 15%w/v, except in the case of the BHN. In the case of SORT, there was a substantial increase in the responses above 120 hours, except once again for BHN. Above 120 hours the matrix became loose due to extensive infiltration and crystallization of salt ions. The interactions plots indicated that the changes among the different factor levels were found to be significant (p 0.05). The average p-values for the changes between levels for each response were: BHN - p 0.035, moisture absorption - p 0.029, gel thickness - p 0.011, and erosion - p 0.042. This technology may be applicable in the development of membrane scaffolds for interconnecting tissues via their role in cell seeding, adhesion and regeneration.

Adsorption and release of active species into and from multifunctional ionic microgel particles

We synthesize monodisperse ionic microgel particles which undergo a large change in volume in response to environmental stimuli such as pH and temperature. In addition, the study elucidates the effective uptake and release of rheology modifiers from these microgel particles to alter the bulk viscosity of a surrounding fluid. Moreover, we found that the prepared ionic microgel particles can demonstrate abilities to adsorb and repel iron oxide nanoparticles (Fe3O4-NPs) upon pH variation. The extent of the loading of Fe3O4-NPs within the colloidal particles and morphology can be manipulated by tunable interactions between the Fe3O4-NPs and ionic microgel particles.

Influence of plasticizer content on the transition of electromechanical behavior of PVC gel actuator

The actuation performance of plasticized poly(vinyl chloride) (PVC) gel actuators in an electric field depends on their chemical composition and electrical and mechanical properties. The influence of plasticizer (dibutyl adipate) content on electromechanical behavior of PVC gels was investigated by impedance spectroscopy and space charge measurement. By plasticizing the PVC, the dielectric constant and space charge density of PVC gel were drastically increased at 1:2 w/w ratio of PVC to plasticizer. To apply the results obtained from the impedance spectroscopy and space charge measurement, electrostatic adhesive forces generated between the PVC gel and the anode were measured. The electrostatic adhesive force at the anode was also dramatically increased at the same plasticizer content. All of the results indicated a transition of electromechanical behavior of PVC gel in the electric field, which was considered to originate from the orientation of polarized plasticizer molecules and dipole rotation of PVC chains. By using the electrostatic adhesive force of PVC gel derived from the electromechanical transition, a new electroactive actuator can be developed for novel applications.

Both core- and shell-cross-linked nanogels: photoinduced size change, intraparticle LCST, and interparticle UCST thermal behaviors

New thermal- and photoresponsive core-shell nanogel particles were obtained from self-assembly in aqueous solution of a double-hydrophilic block copolymer (DHBCP) of which the two blocks could be photo-cross-linked via the reversible photodimerization and photocleavage of coumarin moieties. The diblock copolymer, consisting of poly[N,N-dimethylacrylamide-co-4-methyl-[7-(methacryloyl)oxyethyloxy]coumarin] and poly[N-isopropylacrylamide-co-4-methyl-[7-(methacryloyl)oxyethyloxy]coumarin] (P(DMA-co-CMA)-b-P(NIPAM-co-CMA)), was synthesized by using reversible addition-fragmentation chain transfer (RAFT) polymerization. At T > LCST of the P(NIPAM-co-CMA) block, core-shell micelles were formed and UV light irradiation at λ > 310 nm resulted in cross-linking of both the micelle core of P(NIPAM-co-CMA) and the micelle shell of P(DMA-co-CMA); subsequent cooling of the solution to T < LCST gave rise to water-soluble, swollen nanogel particles. Upon UV light irradiation at λ < 260 nm, the decrease of cross-linking density could increase the swelling of nanogel particles by ∼23% in diameter. By alternating irradiation with the different wavelengths, the average hydrodynamic diameter of nanogel particles was tunable between ∼58 and ∼47 nm. Interestingly, upon further cooling of the solution, aggregation occurred for nanogel particles with a moderate cross-linking density (10%-40% dimerization of coumarin moieties). Therefore, such core- and shell-cross-linked nanogel could display both "intraparticle" LCST (solubility of polymer chains forming the core) and "interparticle" UCST (solubility of particles). The possible mechanism and the effect of dimerization degree on the UCST behavior were discussed.

Tunable nanolubrication between dual-responsive polyionic grafts

This study reports on a direct approach of quantitatively probing the nanotribological response of chemically end-grafted polyions. A combination of a quartz crystal microbalance with dissipation and atomic force microscopy, in the now well established colloidal probe mode, was utilized to investigate the stimuli-induced lubrication behavior between poly(2-(dimethylamino)ethyl methacrylate) grafts on gold. Force and friction measurements showed reversible transitions of up to an order of magnitude difference induced by varying the solvent conditions. The greatly enhanced lubrication observed at low pH was attributed to the formation of a repulsive, highly charged, hydrated cushion. At high pH the friction was significantly increased. The system turned attractive above the lower critical solution temperature with a small friction reduction interpreted as being due to nanoscopic flattening at the interfacial boundary.