Conformational Parameters and Hydrodynamic Behavior of Poly(2-Methyl-2-Oxazoline) in a Broad Molar Mass Range.

In this work, we report our results on the hydrodynamic behavior of poly(2-methyl-2-oxazoline) (PMeOx). PMeOx is gaining significant attention for use as hydrophilic polymer in pharmaceutical carriers as an alternative for the commonly used poly(ethylene glycol) (PEG), for which antibodies are found in a significant fraction of the human population. The main focus of the current study is to determine the hydrodynamic characteristics of PMeOx under physiological conditions, which serves as basis for better understanding of the use of PMeOx in pharmaceutical applications. This goal was achieved by studying PMeOx solutions in phosphate-buffered saline (PBS) as a solvent at 37 °C. This study was performed based on two series of PMeOx samples; one series is synthesized by conventional living cationic ring-opening polymerization, which is limited by the maximum chain length that can be achieved, and a second series is obtained by an alternative synthesis strategy based on acetylation of well-defined linear poly(ethylene imine) (PEI) prepared by controlled side-chain hydrolysis of a defined high molar mass of poly(2-ethyl-2-oxazoline). The combination of these two series of PMeOx allowed the determination of the Kuhn-Mark-Houwink-Sakurada equations in a broad molar mass range. For intrinsic viscosity, sedimentation and diffusion coefficients, the following expressions were obtained: η=0.015M0.77, s0=0.019M0.42 and D0=2600M-0.58, respectively. As a result, it can be concluded that the phosphate-buffered saline buffer at 37 °C represents a thermodynamically good solvent for PMeOx, based on the scaling indices of the equations. The conformational parameters for PMeOx chains were also determined, revealing an equilibrium rigidity or Kuhn segment length, (A) of 1.7 nm and a polymer chain diameter (d) of 0.4 nm. The obtained value for the equilibrium rigidity is very similar to the reported values for other hydrophilic polymers, such as PEG, poly(vinylpyrrolidone) and poly(2-ethyl-2-oxazoline), making PMeOx a relevant alternative to PEG.

Pullulan-Graft-Polyoxazoline: Approaches from Chemistry and Physics.

An approach to the preparation of pullulan-graft-poly(2-methyl-2-oxazoline)s based on Cu-catalyzed azide-alkyne cycloaddition with polyoxazoline-azide was applied. All of the obtained polymers were characterized through classical molecular hydrodynamic methods and NMR. The formation of graft copolymers was accomplished by oxidative degradation of pullulan chains. Nevertheless, graft copolymers were obtained as uniform products with varied side chain lengths and degrees of substitution.

Amphiphilic Diblock Copolymers Bearing Poly(Ethylene Glycol) Block: Hydrodynamic Properties in Organic Solvents and Water Micellar Dispersions, Effect of Hydrophobic Block Chemistry on Dispersion Stability and Cytotoxicity.

Despite the fact that amphiphilic block copolymers have been studied in detail by various methods both in common solvents and aqueous dispersions, their hydrodynamic description is still incomplete. In this paper, we present a detailed hydrodynamic study of six commercial diblock copolymers featuring the same hydrophilic block (poly(ethylene glycol), PEG; degree of polymerization is ca. 110 ± 25) and the following hydrophobic blocks: polystyrene, PS35-b-PEG115; poly(methyl methacrylate), PMMA55-b-PEG95; poly(1,4-butadyene), PBd90-b-PEG130; polyethylene PE40-b-PEG85; poly(dimethylsiloxane), PDMS15-b-PEG115; and poly(ɛ-caprolactone), PCL45-b-PEG115. The hydrodynamic properties of block copolymers are investigated in both an organic solvent (tetrahydrofuran) and in water micellar dispersions by the combination of static/dynamic light scattering, viscometry, and analytical ultracentrifugation. All the micellar dispersions demonstrate bimodal particle distributions: small compact (hydrodynamic redii, Rh ≤ 17 nm) spherical particles ascribed to "conventional" core-shell polymer micelles and larger particles ascribed to micellar clusters. Hydrodynamic invariants are (2.4 ± 0.4) × 10-10 g cm2 s-2 K-1 mol-1/3 for all types of micelles used in the study. For aqueous micellar dispersions, in view of their potential biomedical applications, their critical micelle concentration values and cytotoxicities are also reported. The investigated micelles are stable towards precipitation, possess low critical micelle concentration values (with the exception of PDMS15-b-PEG115), and demonstrate low toxicity towards Chinese Hamster Ovarian (CHO-K1) cells.

Hydrodynamic Characteristics and Conformational Parameters of Ferrocene-Terpyridine-Based Polymers.

Nowadays, the study of metallopolymers is one of the fastest growing areas of polymer science. Metallopolymers have great potential for application in multiple technological and various biomedical processes. The macromolecules with the possibility of varying the number and type of metal ions along the entire length of the polymer chain are of particular interest. In this regard, this study presents results on two successfully synthesized homopolymers, random and block copolymers based on PMMA, containing ferrocene and terpyridine moieties in the side chain. Different architectures of copolymers may attribute interesting properties when creating complexes with various metal ions. A detailed hydrodynamic study of these structures was carried out, the consistency of hydrodynamic data was established using the concept of a hydrodynamic invariant, the absolute values of the molar masses of the studied objects were calculated, and the conformational parameters of macromolecules were determined. Using the Fixman-Stockmayer theory, the equilibrium rigidities of the studied systems were calculated and the relationship between the chemical structure and conformational characteristics was established. The studied copolymers can be attributed to the class of flexible-chain macromolecules. An increase in the equilibrium rigidity value with an increase of the side chain, which is characteristic of comb-shaped polymers, was determined.

Self-Assembled Quaternary Ammonium-Containing Comb-Like Polyelectrolytes for the Hydrolysis of Organophosphorous Esters: Effect of Head Groups and Counter-Ions.

The aim of this work was to increase the efficiency of catalytic systems for the hydrolytic cleavage of 4-nitrophenyl esters of phosphonic acids. Quaternary ammonium-containing comb-like polyelectrolytes («polymerized micelles¼) with ester cleavable fragments and a low aggregation threshold were used as catalysts. The synthesis of poly(11-acryloyloxyundecylammonium) surfactants with different counterions (Br- , NO3- , CH3 C6 H4 SO3- ) and head groups was realized by micellar free-radical polymerization. Molecular weight, critical association concentration, particle sizes and solubilization properties toward Orange OT were determined. Self-assemblies organized by poly(11-acryloyloxyundecyltrimethyl ammonium) bromide successfully catalyze the hydrolysis of 4-nitrophenyl butylchloromethylphosphonate up to two orders of magnitude compared to aqueous alkaline hydrolysis. The development of these catalysts is promising for industrial applications and organophosphorus compound detoxification.

Stabilization of Silver Nanoparticles by Cationic Aminoethyl Methacrylate Copolymers in Aqueous Media-Effects of Component Ratios and Molar Masses of Copolymers.

The ability of aminoethyl methacrylate cationic copolymers to stabilize silver nanoparticles in water was investigated. Sodium borohydride (NaBH4) was employed as a reducing agent for the preparation of silver nanoparticles. The objects were studied by ultraviolet-visible (UV-vis) spectroscopy, dynamic light scattering (DLS), analytical ultracentrifugation (AUC) and scanning electron microscopy (SEM). Formation of nanoparticles in different conditions was investigated by varying ratios between components (silver salt, reducing agent and polymer) and molar masses of copolymers. As a result, we were successful in obtaining nanoparticles with a relatively narrow size distribution that were stable for more than six months. Consistent information on nanoparticle size was obtained. The holding capacity of the copolymer was studied.