pH-dependence of the properties of hydrophobically modified polyvinylamine

Magnetic nanoparticle embedded chitosan-based polymeric network for the hydrophobic drug delivery of paclitaxel

Safe delivery of hydrophobic drugs to the tumor site is a major problem for the scientific community. To improve the in vivo efficacy of hydrophobic drugs by avoiding solubility concerns and providing targeted delivery by nanoparticle, we have developed robust iron oxide nanoparticles coated chitosan with ([2- (methacryloyloxy) ethyl] trimethyl ammonium chloride) (METAC) [CS-IONPs-METAC-PTX] as a drug carrier for the delivery of hydrophobic drug, paclitaxel (PTX). Drug carrier was characterized using various techniques like FT-IR, XRD, FE-SEM, DLS and VSM. Maximum drug release of 93.50 ± 2.80 % from CS-IONPs-METAC-PTX occurs at pH 5.5 in 24 h. Significantly, the nanoparticles exhibited excellent therapeutic efficacy when appraised in L929 (Fibroblast) cell lines with a good cell viability profile. CS-IONPs-METAC-PTX shows excellent cytotoxic effect in MCF-7 cell lines. In 100 μg/mL concentration, CS-IONPs-METAC-PTX formulation shows 13.46 ± 0.40 % of cell viability. Selectivity index of 2.12 indicates the highly selective and safe performance of CS-IONPs-METAC-PTX. Admirable hemocompatibility of the developed polymer material demonstrating its applicability towards drug delivery. Results of the investigation substantiate that the prepared drug carrier is a potent material for the delivery of PTX.

Molecular dynamics simulations of structure and dynamics in aqueous solution of neutral and ionized derivatives of poly(F): methyl, n-propyl, and isopropyl substitutions

Chain dimensions, intermolecular structure and hydration of a series of uncharged and cationic poly(vinyl amine) [PVAm] linear polymers having hydrophobic substituent methyl, n-propyl, and isopropyl in the monomer are studied in aqueous solution by molecular dynamics simulations. A conformational transition occurs in the degree of ionization, α, range 0.3 to 0.4. Among the polymers studied, isopropyl substituted PVAm is most hydrophobic and methyl substituted PVAm is the least. The extent of hydrophobicity of the chemical structure is directly correlated to the size of the polymer chain. Conformational dynamics become slower with increase in the degree of charge of the chain and with the size of the substituent side group. The significant hydration of the polymers takes place for 0 ≤ α ≤ 0.5. While the number of H-bonds is not affected significantly by the chemical structure of the chain the relaxation dynamics of polymer-water H-bonds is significantly affected, with the more hydrophobic polymer showing the slowest dynamics. The steric hindrance provided by the hydrophobic substituent groups is responsible for slowing of water orientation dynamics in the vicinity of the polymer. The counter-ion condensation is clearly better and the bound water content is less for the relatively more hydrophobic polymer. The overall behavior of structure and dynamics is in qualitative agreement with that known for other types of polyelectrolytes and solutes in aqueous solution.

Influence of Hydrophobicity of Backbone Polymer in Thermo-responsive Hydrogel with Immobilized Amine on Cycle Capacity for Absorption and Recovery of CO2

The chemisorption process with amines is the major separation and recovery method of CO2 because of its high processing capacity and simplicity. However, large energy consumption for the desorption of CO2 is also associated with the process. To develop a separation and recovery process that is capable of desorbing CO2 at low temperatures and with minimal energy consumption, polymer hydrogels with a lower critical solution temperature (LCST) polymer network and amine groups immobilized in the polymer network of the hydrogels were exploited. Thermo-responsive amine gels with a series of hydrophobicity of polymer networks were systematically synthesized, and the influence of the hydrophobicity of the gels on the CO2 desorption temperature and cycle capacity (CO2 amount that can be separated and recovered by 1 cycle of temperature swing operation) was investigated using slurries with the series of gels. A significant decrease in the CO2 desorption temperature and increase in the cycle capacity occurred simultaneously by lowering the LCST of the gels via hydrophobisation of the polymer network. Based on an equilibrium adsorption model representing the CO2 separation and a recovery system with the gel slurries, an analysis of the system dynamics was performed in order to understand the recovery mechanism in the process.

Effect of Water Interactions on Polyvinylamine at Different pHs for Membrane Gas Separation

In our previous work, it was shown that the separation performance of the fixed-site-carrier polyvinylamine (PVAm) composite membrane increases exponentially with increasing relative humidity content in the gas. Through these efforts, it has been important to develop a greater understanding of the relationship between the water, structural, and interfacial properties of the PVAm surface. The degree of hydrophilicity of a given surface plays a crucial role in the separation performance of the membrane when exposed to a humidified gas. Therefore, in the current work, the wettability properties of PVAm at different pHs have been studied by experimental measurements and molecular dynamic simulations. It was confirmed that the intramolecular interactions are not linearly dependent on pH. As well as the H-bonding between protonated and unprotonated amine groups, the conformation polymer chain and the distribution charge density play a crucial role in the surface stability and wettability properties.

Covalently Connecting Crystal Grains with Polyvinylammonium Carbochain Backbone To Suppress Grain Boundaries for Long-Term Stable Perovskite Solar Cells

Grain boundaries act as rapid pathways for nonradiative carrier recombination, anion migration, and water corrosion, leading to low efficiency and poor stability of organometal halide perovskite solar cells (PSCs). In this work, the strategy suppressing the crystal grain boundaries is applied to improve the photovoltaic performance, especially moisture-resistant stability, with polyvinylammonium carbochain backbone covalently connecting the perovskite crystal grains. This cationic polyelectrolyte additive serves as nucleation sites and template for crystal growth of MAPbI₃ and afterward the immobilized adjacent crystal grains grow into the continuous compact, pinhole-free perovskite layer. As a result, the unsealed PSC devices, which are fabricated under low-temperature fabrication protocol with a proper content of polymer additive PVAm·HI, currently exhibit the maximum efficiency of 16.3%. Remarkably, these unsealed devices follow an "outside-in" corrosion mechanism and respectively retain 92% and 80% of the initial PCE value after being exposed under ambient environment for 50 days and 100 days, indicating the superiority of carbochain polymer additives in solving the long-term stability problem of PSCs.

Endowing a cationic hydrophobic associating polyacrylamide solution with CO2 switchable properties using N,N-dimethylolamidopropylamine via the assembly transition between vesicles and spherical micelles by CO2

Endowing a polyacrylamide solution with CO₂ switchable properties using N,N-dimethylolamidopropylamine via the assembly transition between vesicles and spherical micelles.

Far beyond primary poly(vinylamine)s through free radical copolymerization and amide hydrolysis

Copolymers bearing various amino groups of predictable compositions are made available through radical copolymerization followed by optimized amide hydrolysis.

Hydrophobically-modified poly(vinyl pyrrolidone) as a physically-associative, shear-responsive ophthalmic hydrogel

The potential of hydrophobically-modified poly(vinyl pyrrolidone) as a shear-responsive, self-associative hydrogel for ophthalmic applications is demonstrated. Hydrophobic modification was achieved via random copolymerization of N-vinylpyrrolidone with N-vinylformamide, the latter of which can be hydrolyzed to expose a desired degree of reactive amine groups permitting grafting of alkyl chlorides of varying alkyl chain lengths. The resulting materials formed highly shear-responsive physical hydrogels, exhibiting tunable shear thinning over 4-5 decades of viscosity from infinite shear to zero shear conditions that facilitates lubrication upon blinking and/or facile injection or drop-based delivery to the anterior or posterior segments of the eye. Viscosity changes due to self-association over time can also be tuned by changing the length of the hydrophobe, with C18-grafted materials exhibiting prolonged thickening over several weeks to form extremely stiff hydrogels and shorter grafts equilibrating significantly faster but forming weaker gels. The hydrogels remained transparent even at very high polymer concentrations (20 wt%) and are demonstrated to facilitate controlled release of a model drug (doxorubicin). The polymers exhibit minimal cytotoxicity in vitro to human corneal epithelial cells and retinal pigment epithelial cells, particularly when lower molecular weight backbone polymers were used. In vivo assessments in rabbits indicated no significant conjunctival edema or redness, secretion, corneal opacity, or iris involvement upon anterior application. Following intravitreal injection in rat eyes, no opacification of the lens, cornea or vitreous, nor any morphological or functional change to the posterior segment was observed. Examination of wholemount tissues and histology demonstrated no adverse effect from the injection or deposition of material. As such, these shear-thinning materials offer potential for drug delivery in both the anterior and posterior segments or as a vitreal replacement that can be easily administered or removed.

Polyvinylamine: a tool for engineering interfaces

With the highest content of primary amine functional groups of any polymer, polyvinylamine (PVAm) is a potent tool for the modification of macroscopic and nanoparticle surfaces. Based on the free radical polymerization and subsequent hydrolysis of N-vinylformamide, PVAm is prepared as linear polymers (0.8 kDa to >1 MDa), microgels, macrogels, and copolymers. The amine groups serve as reaction sites for grafting PVAm to surfaces and for the preparation of derivatives. Coupling low-molecular-weight molecules and oligomers gives PVAm-X, where X includes hydrophobes, carbohydrate oligomers, proteins, TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy), phenylboronic acids, and fluorocarbons. This contribution highlights the use of PVAm and PVAm-X to modify solid surface properties. Where possible, the PVAm properties and applications as an interfacial agent are compared to those of linear polyethylenimine, polyallylamine, and chitosan.

Photodynamic treatment: a novel method for sanitation of food handling and food processing surfaces

The photodynamic bactericidal effect of the photoactive dyes acriflavine neutral, rose bengal, phloxine B, and malachite green (oxalate salt) at concentrations of 5 to 5,000 microg/ml against two gram-negative strains (Escherichia coli LJH 128 and Salmonella Typhimurium C1058), two gram-positive strains (Bacillus sp. C578 and Listeria monocytogenes LJH 375), and yeast (Saccharomyces cerevisiae C1172) was investigated. Incubation of the investigated bacteria with acriflavine neutral under illumination resulted in a significant reduction in cell numbers compared with dark incubation. Rose bengal caused a significant killing effect for bacteria incubated both in the dark and under illumination. Malachite green was active against gram-positive bacteria under illumination and did not affect gram-negative bacteria or yeasts. Incubation with phloxine B resulted in a significant decline in cell numbers for gram-positive bacteria, both in the dark and under illumination; gram-negative bacteria and yeasts were unaffected. Conjugation of rose bengal and phloxine B with poly(vinyl amine) resulted in an enhanced bactericidal effect during both dark and light incubation. This was explained by electrostatic interaction of the polymer with the cell surface, which resulted in closer contact of the photoactive dye and cell. No killing effect was observed for yeasts incubated with dye conjugates. Filter paper treated with dye-poly(vinyl amine) conjugates showed high photodynamic bactericidal activity against the bacterial strains, but not against the yeasts. The extent of bacterial killing depended on the nature and concentration of the dye conjugate and the type of microorganism. The presented data suggest that a photodynamic approach for constructing "self-decontaminating" materials has potential.

Interactions of hydrophobically modified polyvinylamine with pluronic triblock copolymer micelles

The heats associated with the addition of triblock copolymers of ethylene oxide and propylene oxide (PEO-PPO-PEO pluronics) to solutions of linear polyvinylamine, with N-substituted pendant octyl groups (HMPVAm), were measured as functions of pH and pluronic structure. The interactions were exothermic with the overall enthalpy decreasing with increasing pH from 5 to 10. Surprisingly, the heat effect increased with increasing pluronic hydrophilicity; however, no enthalpy change was observed in the absence of micelles. The results were quantitatively modeled by assuming two competing processes-micellar dissolution and HMPVAm coating of micelles, preventing dissolution.