Andrzej Dworak

Dihydrophilic block copolymers with ionic and nonionic blocks. I. Poly(ethylene oxide)-b-polyglycidol with OP(O)(OH)2, COOH, or SO3H functions: Synthesis and influence for CaCO3 crystallization

Dihydrophilic block copolymers of poly(ethylene oxide)-b-polyglycidol were prepared and polyglycidol blocks converted into ionic blocks containing OP(O)(OH)2, COOH, or SO3H groups. Although phosphorylation of polyhydroxy compounds with POCl3 usually leads to insoluble products, phosphorylation of poly(ethylene oxide)-b-polyglycidol using a POCl3/OH ratio equal to 1/1 gave soluble products, predominantly monoester of phosphoric acid (after hydrolysis) (provided that the reaction was conducted in triethyl phosphate as solvent). All copolymers were characterized by 1H NMR, 13C NMR, and/or 31P NMR spectra for confirming their structure. The degree of substitution was determined from quantitative 13C NMR spectroscopy (inverted-gate decoupling-acquisition mode). Preliminary results indicate that from these three groups of block copolymers the phosphoric acid esters are the most effective ones at least in controlling the growth of CaCO3 crystals in aqueous solution.

Polyglycidol-block-poly(ethylene oxide)-block-polyglycidol: synthesis and swelling properties

Triblock copolymers containing central poly(ethylene oxide) blocks and polyglycidol side chains were synthesized using cesium polyoxyethylene glycolates as macroinitiators. Water soluble copolymers containing central blocks of 40 to 230 structural poly(ethylene oxide) units and side chains of 30 to 70 polyglycidol units and relatively narrow molecular weight distribution were obtained. The copolymers were crosslinked with glutar aldehyde and their swelling in water and methanol was investigated.

The role of cationic and covalent active centers in the polymerization of 2-methyl-2-oxazoline initiated with benzyl bromide

It was shown that in the polymerization of 2-methyl-2-oxazoline initiated with benzyl bromide in nitrobenzene the equilibrium constant of the interconversion of cationic and covalent active centers could be measured over a wide range of temperatures, thus making the thermodynamic parameters of this reaction available. The temperature jump method was used to measure the rate constants and the activation parameters of the reversible transformation of the ionic active centers into covalent ones. The apparent rate constant of the chain growth in this polymerization was measured, and individual rate constants of chain growth on ionic and covalent centers were approximated using systems in which one kind of active centers strongly prevails. The obtained data allowed for a complete description of the individual reactions and for an estimation of the contribution of these reactions to chain growth. Because of the higher reactivity of the ionic species and higher rate of ionization without monomer participation (thus, through intramolecular ionization), there are no conditions at which the covalent species may prevail in the chain growth. Even if there is a large excess of covalent species, propagation proceeds on the ionic ones. The effective monomer concentration is approximately 10 3 mol/L, indicating that at 1 mol/L of monomer the internal ionization proceeds 10 3 times faster than the external ionization (with monomer).

Poly[tri(ethylene glycol) ethyl ether methacrylate]-coated surfaces for controlled fibroblasts culturing.

Well-defined thermosensitive poly[tri(ethylene glycol) monoethyl ether methacrylate] (P(TEGMA-EE)) brushes were synthesized on a solid substrate by the surface-initiated atom transfer radical polymerization of TEGMA-EE. The polymerization reaction was initiated by 2-bromo-2-methylpropionate groups immobilized on the surface of the wafers. The changes in the surface composition, morphology, philicity, and thickness that occurred at each step of wafer functionalization confirmed that all surface modification procedures were successful. Both the successful modification of the surface and bonding of the P(TEGMA-EE) layer were confirmed by X-ray photoelectron spectroscopy (XPS) measurements. The thickness of the obtained P(TEGMA-EE) layers increased with increasing polymerization time. The increase of environmental temperature above the cloud point temperature of P(TEGMA-EE) caused the changes of surface philicity. A simultaneous decrease in the polymer layer thickness confirmed the thermosensitive properties of these P(TEGMA-EE) layers. The thermosensitive polymer surfaces obtained were evaluated for the growth and harvesting of human fibroblasts (basic skin cells). At 37 °C, seeded cells adhered to and spread well onto the P(TEGMA-EE)-coated surfaces. A confluent cell sheet was formed within 24 h of cell culture. Lowering the temperature to an optimal value of 17.5 °C (below the cloud point temperature of the polymer, TCP, in cell culture medium) led to the separation of the fibroblast sheet from the polymer layer. These promising results indicate that the surfaces produced may successfully be used as substrate for engineering of skin tissue, especially for delivering cell sheets in the treatment of burns and slow-healing wounds.

Polymeric nanoparticle engineering: from temperature-responsive polymer mesoglobules to gene delivery systems.

A novel approach for the preparation of nano- and microcapsules in aqueous solutions by using thermoresponsive polymer (TRP) templates (mesoglobules) is described. The method comprised three steps: formation of mesoglobules, coating the templates by seeded radical copolymerization, followed by core dissolution and core removal upon cooling. When mesoglobule entraps biomacromolecules during the process of their formation, it makes it possible to load a controlled amount of bioactive compounds without covalent attachment. Special attention is paid to the mesoglobule dissolution upon cooling, as well as their loading efficiency. Details on the outer shell formation and the possibilities for targeting ligands incorporation and control of the shell porosity are discussed. Finally, the seeded radical copolymerization was used for covering DNA complexes with cationic copolymers bearing TRP blocks. This Review is an attempt to convince researchers of the promising perspectives for using mesoglobules as potential reservoirs, carriers, and transferring agents for biologically active substances.

Polyether nanoparticles from covalently crosslinked copolymer micelles.

Double hydrophilic block copolymers poly(ethylene oxide)-b-polyglycidol were synthesized using living anionic polymerization. The polyglycidol blocks were made hydrophobic by the esterification of a part of hydroxyl groups with cinnamic acid, thus simultaneously attaching UV-sensitive double bonds to the polymer backbone. The block copolymers were found to spontaneously associate in aqueous solution forming well-defined micelles, where the corona of the micelles was formed of EO units and the cores consisted of hydrophobic glycidyl cinnanamate units. The critical micelle concentration was determined by light-scattering measurements and fluorescence spectroscopy. Stabilization of micelles was obtained by covalently crosslinking the cores of polyether micelles formed from amphiphilic block copolymers of the type poly(ethylene oxide)-b-poly(glycidol-co-glycidyl cinnamate) (denoted EO(113)-b-(Gl(33)-co-GlCA(33-x))). To obtain stable nanoparticles double bonds of cinnamate units contained in core were crosslinked under UV irradiation. The kinetics of the stabilization process was investigated using SEC-MALLS and UV spectroscopy. The parameters of the micelles and nanogels were calculated from the light-scattering data.

Cytotoxicity, haematotoxicity and genotoxicity of high molecular mass arborescent polyoxyethylene polymers with polyglycidol-block-containing shells

We have examined the impact on biological systems of some newly synthesised polyoxyethylene polymers using in vitro assays. Toxicity was tested by the 3‐[4,5‐dimethylthiazole‐2‐yl]‐2,5 diphenyltetrazolium bromide (MTT) assay, haemolysis was assessed, and an ethidium bromide (EB) assay was used to study interactions between the polymers and DNA. All the assay data showed that the polymers are biocompatible. No differences were found between generations (i.e. macromolecule sizes). The results encourage continuing studies on the clinical use of these molecules as drug carriers.

Investigation of the structure of poly(p-chlorophenyl glycidyl ether) by the 13C n.m.r. technique: tacticity and addition isomerism

Abstract The p -chlorophenyl glycidyl ether was polymerized in the presence of Al(OiPr) 3 , ZnCl 2 , SnCl 4 , BuOK, KOH and by the Al(OiPr) 3 ZnCl 2 1:1 initiator system. Analysis of the 13 C n.m.r. spectra of the poly( p -chlorophenyl glycidyl ethers) obtained has made it possible to determine their tacticity and the content of the head-to-tail and head-to-head linkages in the polymer chain.

Oxirane ring opening and polymer structure in the polymerization of styrene oxide initiated by aluminium isopropoxide

Abstract In the Al(OiPr)3 initiated polymerization of styrene oxide, a relatively high molecular weight, head-to-tail polymer is obtained with some oligomers. Study of the polymerization and model reactions of R(+)-styrene oxide initiated by Al(OiPr)3 indicates that, unlike the case of anionic polymerization, the oxirane ring is opened exclusively at the α-position (cleavage of the CHO-bond), a process which is accompanied by inversion of the configuration of the tertiary carbon atom.

Controlling the Crystallinity of Thermoresponsive Poly(2-oxazoline)-Based Nanolayers to Cell Adhesion and Detachment

Semicrystalline, thermoresponsive poly(2-isopropyl-2-oxazoline) (PIPOx) layers covalently bonded to glass or silica wafers were obtained via the surface-termination of the living polymer chains. Polymer solutions in acetonitrile were exposed to 50 °C for various time periods and were poured onto the functionalized solid wafers. Fibrillar crystallites formed in polymerization solutions settled down onto the wafers next to the amorphous polymer. The amount of crystallites adsorbed on thermoresponsive polymer layers depended on the annealing time of the PIPOx solution. The wettability of PIPOx layers decreased with the increasing amount of crystallites. The higher content of crystallites weakened the temperature response of the layer, as evidenced by the philicity and thickness measurements. Semicrystalline thermoresponsive PIPOx layers were used as biomaterials for human dermal fibroblasts (HDFs) culture and detachment. The presence of crystallites on the PIPOx layers promoted the proliferation of HDFs. Changes in the physicochemical properties of the layer, caused by the temperature response of the polymer, led to the change in the cells shape from a spindle-like to an ellipsoidal shape, which resulted in their detachment. A supporting membrane was used to assist the detachment of the cells from PIPOx biosurfaces and to prevent the rolling of the sheet.