Synthesis and self-association in aqueous media of poly(ethylene oxide)/poly(ethyl glycidyl carbamate) amphiphilic block copolymers

Influence of hydrophilic block length on the aggregation properties of polyglycidol-polystyrene-polyglycidol copolymers

Amphiphilic triblock copolymers, polyglycidol-polystyrene-polyglycidol (PGL-PS-PGL), were synthesised via anionic polymerization starting from the synthesis of a polystyrene macroinitiator with 60 styrene units in the block terminated by ethylene oxide. Poly(ethoxyethyl glycidyl ether) blocks of different lengths were created on both sides of the macroinitiator. By removing the ethoxyethyl blocking groups, PGL-PS-PGL copolymers containing polyglycidol blocks with DP 11, 23, 44 and 63 were received. Their structures were determined by NMR and FTIR. The hydrophilicity of PLG-PS-PGL films was studied upon exposure to water vapour. To perform the copolymers' aggregation in water, the samples were dialysed from DMF into water. The critical concentration of their micellisation (CMC) was determined by measuring the absorbance of the 1,6-diphenylhexa-1,3,5-triene (DPH) probe and the intensity of light scattered by the copolymers' solution as a function of concentration. CMC values increased with increasing the number of hydrophilic glycidol units in the copolymer chain. The sizes of aggregates formed slightly above the critical concentration were measured by dynamic light scattering (DLS), and particles were imaged by cryo-TEM. Cryo-TEM pictures showed the presence of regular micelles in copolymer dispersions. For copolymers with shorter PGL chains aggregated partices were detected. Moreover, cryo-TEM demonstrated that the copolymers with a polyglycidol block of DP = 63 formed regular spherical micelles that formed 2D ordered organisation on the surface. X-ray measurements showed the formation of a partially crystallised PS core in the micelle's interior. The aggregates of all copolymers were stable. Their sizes did not change after one year of storage. The particles did not disassociate even after diluting their dispersions to a concentration 10 times lower than the critical concentration.

Synthesis, Hydrophilicity and Micellization of Coil-Brush Polystyrene-b-(polyglycidol-g-polyglycidol) Copolymer-Comparison with Linear Polystyrene-b-polyglycidol

In this paper, an original method of synthesis of Coil-Brush amphiphilic polystyrene-b-(polyglycidol-g-polyglycidol) (PS-b-(PGL-g-PGL)) block copolymers was developed. The hypothesis that their hydrophilicity and micellization can be controlled by polyglycidol blocks architecture was verified. The research enabled comparison of behavior in water of PS-b-PGL copolymers and block-brush copolymers PS-b-(PGL-g-PGL) with similar composition. The Coil-Brush copolymers were composed of PS-b-PGL linear core with average DPn of polystyrene 29 and 13 of polyglycidol blocks. The DPn of polyglycidol side blocks of coil-b-brush copolymers were 2, 7, and 11, respectively. The copolymers were characterized by 1H and 13C NMR, GPC, and FTIR methods. The hydrophilicity of films from the linear and Coil-Brush copolymers was determined by water contact angle measurements in static conditions. The behavior of Coil-Brush copolymers in water and their critical micellization concentration (CMC) were determined by UV-VIS using 1,6-diphenylhexa-1,3,5-trien (DPH) as marker and by DLS. The CMC values for brush copolymers were much higher than for linear species with similar PGL content. The results of the copolymer film wettability and the copolymer self-assembly studies were related to fraction of hydrophilic polyglycidol. The CMC for both types of polymers increased exponentially with increasing content of polyglycidol.

The Role of Polymer Structure in Formation of Various Nano- and Microstructural Materials: 30 Years of Research in the Laboratory of Nano- and Microstructural Materials at the Centre of Polymer and Carbon Materials PAS

The review summarizes the research carried out in the Laboratory of Nano- and Microstructural Materials at the Centre of Polymer and Carbon Materials, Polish Academy of Sciences (CMPW PAS). Studies carried out for many years under the guidance of Professor Andrzej Dworak led to the development and exploration of the mechanisms of oxirane and cyclic imine polymerization and controlled radical polymerization of methacrylate monomers. Based on that knowledge, within the last three decades, macromolecules with the desired composition, molar mass and topology were obtained and investigated. The ability to control the structure of the synthesized polymers turned out to be important, as it provided a way to tailor the physiochemical properties of the materials to their specific uses. Many linear polymers and copolymers as well as macromolecules with branched, star, dendritic and hyperbranched architectures were synthesized. Thanks to the applied controlled polymerization techniques, it was possible to obtain hydrophilic, hydrophobic, amphiphilic and stimulus-sensitive polymers. These tailor-made polymers with controlled properties were used for the construction of various types of materials, primarily on the micro- and nanoscales, with a wide range of possible applications, mainly in biomedicine. The diverse topology of polymers, and thus their properties, made it possible to obtain various types of polymeric nanostructures and use them as nanocarriers by encapsulation of biologically active substances. Additionally, polymer layers were obtained with features useful in medicine, particularly regenerative medicine and tissue engineering.

Cationic (Co)polymers Based on N-Substituted Polyacrylamides as Carriers of Bio-macromolecules: Polyplexes, Micelleplexes, and Spherical Nucleic Acidlike Structures

Novel N-substituted polyacrylamides bearing a cycle with two tertiary amines, poly(4-methyl-piperazin-1-yl)-propenone (PMPP) and its block copolymers with polylactide (PMPP-b-PLA), are synthesized and characterized. The homopolymers are water-soluble, whereas the block copolymers self-assemble in aqueous solution into a small size (R_h around 30 nm), are narrowly distributed, and exhibit core-shell micelles with good colloidal stability. Both the homopolymers and copolymer micelles are positively charged (ζ-potentials in the 13.8-17.6 mV range), which are employed for formation of electrostatic complexes with oppositely charged DNA. Complexes (polyplexes, micelleplexes, and spherical nucleic acidlike structures) in a wide range of N/P (amino to phosphate groups) ratios are prepared with short (115 bp) and long (2000 bp) DNA. The behavior and physicochemical properties of the resulting nanocarriers of DNA are strongly dependent on the polymer/polymer micelles' characteristics and the DNA chain length. All systems exhibit low cytotoxicity and good cellular uptake ability and show promise for gene delivery and regulation.

Micellization of Polystyrene-b-Polyglycidol in Dioxane and Water/Dioxane Solutions

In this work, the self-assembly of a series of amphiphilic polystyrene-b-polyglycidol (PS-b-PGL) diblock copolymers in dioxane and dioxane/water mixtures is presented. The PS-b-PGL have an average degree of polymerization (DP) of PS block equal to 29 units and varied degrees of polymerization for the glycidol segments with DPs of 13, 42, 69 and 117. In dioxane, amphiphilic diblock copolymers form micelles with the hydrophilic PGL placed in the core. Critical micelle concentration (CMC) was determined based on the intensity of scattered light vs. concentration. The micelle size was measured by dynamic light scattering and transmission electron microscopy. Also, the behaviour of the copolymer was studied in water/dioxane solutions by following the changes of scattered light intensity with the addition of water to the system. Critical water content (CWC) of the studied systems decreased as the initial PS-b-PGL concentration in dioxane increased. This process was accompanied by a decrease in the size of aggregate formed. For a given initial copolymer concentration, the size of copolymer aggregates decreased linearly with increasing the length of the PGL block

Deepening the insight into poly(butylene oxide)-block-poly(glycidol) synthesis and self-assemblies: micelles, worms and vesicles

Aqueous self-assembly of amphiphilic block copolymers is studied extensively for biomedical applications like drug delivery and nanoreactors. The commonly used hydrophilic block poly(ethylene oxide) (PEO), however, suffers from several drawbacks. As a potent alternative, poly(glycidol) (PG) has gained increasing interest, benefiting from its easy synthesis, high biocompatibility and flexibility as well as enhanced functionality compared to PEO. In this study, we present a quick and well-controlled synthesis of poly(butylene oxide)-block-poly(glycidol) (PBO-b-PG) amphiphilic diblock copolymers together with a straight-forward self-assembly protocol. Depending on the hydrophilic mass fraction of the copolymer, nanoscopic micelles, worms and polymersomes were formed as well as microscopic giant unilamellar vesicles. The particles were analysed regarding their size and shape, using dynamic and static light scattering, TEM and Cryo-TEM imaging as well as confocal laser scanning microscopy. We have discovered a strong dependence of the formed morphology on the self-assembly method and show that only solvent exchange leads to the formation of homogenous phases. Thus, a variety of different structures can be obtained from a highly flexible copolymer, justifying a potential use in biomedical applications.

Improved synthesis and well controlled self-assembly of PBO-b-PG amphiphilic diblock copolymers led to homogenous phases of micelles, worms and vesicles.

Photocrosslinking of Polyglycidol and Its Derivative: Route to Thermoresponsive Hydrogels

Hydrogels of biologically well-tolerated, high-molar-mass polyglycidol (PGl) and its thermoresponsive derivative poly(glycidol-co-ethyl glycidyl carbamate) have been obtained by direct UV crosslinking in the solid state. Polymers with molar masses up to 1.45 × 10⁶ g mol^-1 were crosslinked in the presence of benzophenone or (4-benzoylbenzyl)trimethylammonium chloride as photosensitizers. The photosensitizer concentration was varied from 2 to 10 wt%. The influence of polymer composition and photosensitizer type and amount on the crosslinking efficiency, swelling and temperature behavior of the obtained hydrogels was investigated. The photocrosslinking of PGl and poly(glycidol-co-ethyl glycidyl carbamate) led to hydrogels with swelling degrees up to 1700%. The swelling degrees of the hydrogels decreased with the increase of the environmental temperature indicating the thermoresponsive nature of gels. The swelling of obtained gels can be controlled by varying the composition of the copolymer precursor and by the network density.

Hetero-Multifunctional Poly(ethylene glycol) Copolymers with Multiple Hydroxyl Groups and a Single Terminal Functionality

Hetero-multifunctional poly(ethylene glycol-co-glycerol) random copolymers with multiple hydroxyl functionalities and a single terminal functionality have been prepared by copolymerization of ethylene oxide (EO) and ethoxy ethyl glycidyl ether (EEGE) with the use of a suitable initiator, introducing a protected amino group or a double bond, respectively. Acidic deprotection was used for removal of the acetal protecting groups in the chain, and the terminal amino group was regenerated by catalytic hydrogenation. A series of copolymers with narrow polydispersity was obtained, varying comonomer fractions from 3 to 67% and molecular weights in the range of 5 000-32 000 g · mol(-1) (1.05 < $\overline M _{\rm w} /\overline M _{\rm n}$ < 1.25). Molecular and thermal characterization was carried out using (1) H- and (13) C NMR, SEC and differential scanning calorimetry (DSC).