Equilibrium Swelling of Biocompatible Thermo-Responsive Copolymer Gels

Biomedical applications of thermo-responsive (TR) hydrogels require these materials to be biocompatible, non-cytotoxic, and non-immunogenic. Due to serious concerns regarding potential toxicity of poly(N-isopropylacrylamide) (PNIPAm), design of alternative homo- and copolymer gels with controllable swelling properties has recently become a hot topic. This study focuses on equilibrium swelling of five potential candidates to replace PNIPAm in biomedical and biotechnological applications: poly(N-vinylcaprolactam), poly(vinyl methyl ether), poly(N,N-dimethyl amino ethyl methacrylate), and two families of poly(2-oxazoline)s, and poly(oligo(ethylene glycol) methacrylates). To evaluate their water uptake properties and to compare them with those of substituted acrylamide gels, a unified model is developed for equilibrium swelling of TR copolymer gels with various types of swelling diagrams. Depending on the strength of hydrophobic interactions (high, intermediate, and low), the (co)polymers under consideration are split into three groups that reveal different responses at and above the volume phase transition temperature.

Sustainable Synthesis of Vinyl Methyl Ether from Biomass-derived Ethylene Glycol Dimethyl Ether over Solid Base Catalysts

Vinyl methyl ether (VME) is an important chemical intermediate for the production of functional polymers and fine chemicals. It is primarily produced in industry via the addition of methanol to...

Energy Dependent XPS Measurements on Thin Films of a Poly(vinyl methyl ether)/Polystyrene Blend in Dependence on Film Thickness – Concentration Profile on a Nanometer Resolution to Understand the Behavior of Nanofilms

The composition of the surface layer in dependence from the distance of the polymer/air interface in thin films with thicknesses below 100 nm of miscible polymer blends on a spatial...

Phase Equilibrium and Interdiffusion in Poly(Vinyl Methyl Ether)-Water System

The phase state diagram of the poly(vinyl methyl ether)-water system in a wide concentration range was obtained by the optical interferometry method. It was shown that this system was characterized by a complicated phase equilibrium with two lower critical solution temperatures, one of which was located in the concentrated region at 21 °C, and the other one in the region of a dilute solution at 31 °C. In the framework of the Flory–Huggins theory, pair interaction parameters were calculated for different parts of the binodal curves, and an attempt was made to reverse simulate the diagram in different conditions. It was suggested that the unusual character of the diagram was associated with the formation of a complicated complex between PVME and water in the middle region of the compositions. Concentration profiles for different temperatures were constructed. For the first time for this system, the numerical values of the diffusion coefficients of poly(vinyl methyl ether) (PVME) into water and water in PVME were obtained. Concentration and temperature dependences of diffusion coefficients were constructed and analyzed. The kinetics of water sorption in PVME was plotted, the clustering integral was calculated, and the approximate number of molecules in a water cluster was estimated. It was shown that in the dilute solution region upon passing through the binodal curve, the interphase disappeared immediately, and the remaining fluctuation of the concentration decreased in size with time. The kinetics of this process was estimated from the change in the size of such a particle.

DETERMINATION OF THE BIOADHESION INDICATORS OF VAGINAL GEL WITH RESVERATROL AND HYALURONIC ACID

Aim. The purpose of the work is to determine the bioadhesion indices of vaginal gel with resveratrol and hyaluronic acid, as well as the choice of the type and content of mucoadhesives in the composition. Materials and methods. As research objects samples of gels with different mucoadhesives in the composition were used. Among used mucoadhesives were: sodium alginate (FMC BioPolimer AS, Norway), methyl cellulose (Shin Etsu, Germany), Methocel – methyl cellulose with hydroxypropylmethyl cellulose (Dow Pharmaceutical Sciences, USA), OraRez® W-100L16 – vinyl methyl ether and maleic anhydride copolymer (BOAI, China). As a comparison drug, vaginal gel "Gynodec" (Yuriya-Pharm) was used. During the study, the rate of gel distribution, the degree of deformation under the influence of mechanical forces, the degree of the gel fixation on the surface of the mucosa and the adhesion ability of the samples have been determined. Results. The study has determined that sample No. 2 with sodium alginate has the highest distribution rate, which was 1.56 cm/min. The study of the fixation of samples on the surface of the model of the mucous was performed by the method of flow. The results have showed that the sample with sodium alginate has the closest value to the reference drug. The adhesive ability of samples with different sodium alginate contents was determined. The tensimetric study has found that at a concentration of 0.5 %, the force required to separate the surface is 6158 Pa. Conclusions. On the basis of the complex of physico-chemical studies, bioadhesion indicators of vaginal gel with resveratrol, depending on the type and concentration of mucoadhesives have been determined. According to the distribution parameters on the surface of the genital mucosa model, it has been found that the best properties compared with other types of mucoadhesives has a sample containing sodium alginate. The study by means of a strain gauge has found that the addition of sodium alginate at a concentration of 0.5 % would provide a satisfactory adhesive ability of the vaginal gel.

Glass-Transition Dynamics of Mixtures of Linear Poly(vinyl methyl ether) with Single-Chain Polymer Nanoparticles: Evidence of a New Type of Nanocomposite Materials

Single-chain polymer nanoparticles (SCNPs) obtained through chain collapse by intramolecular cross-linking are attracting increasing interest as components of all-polymer nanocomposites, among other applications. We present a dielectric relaxation study on the dynamics of mixtures of poly(vinyl methyl ether) (PVME) and polystyrene (PS)-based SCNPs with various compositions. Analogous dielectric measurements on a miscible blend of PVME with the linear precursor chains of the SCNPs are taken as reference for this study. Both systems present completely different behaviors: While the blend with the linear precursor presents dynamics very similar to that reported for PVME/PS miscible blends, in the PVME/SCNP mixtures there are an appreciable amount of PVME segments that are barely affected by the presence of SCNPs, which nearly vanishes only for mixtures with high SCNP content. Interestingly, in the frame of a simple two-phase system, our findings point towards the existence of a SCNP-rich phase with a constant PVME fraction, regardless of the overall concentration of the mixture. Moreover, the dynamics of the PVME segments in this SCNP-rich phase display an extreme dynamic heterogeneity, a signature of constraint effects.