Thermosensitive dendritic stars of tert-butyl-glycidylether and glycidol – Synthesis and encapsulation properties

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.

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.

Thermoresponsive Nanogels of Modified Poly((di(ethylene glycol) methyl ether methacrylate)-co-(2-aminoethyl methacrylate))s

A series of copolymers of di(ethylene glycol) methyl ether methacrylate (D) and 2-aminoethyl methacrylate (A) (P(D-co-A)) with variable ratios of comonomers were synthesized using atom transfer radical polymerization. Then, the amino groups of obtained copolymers were modified to clickable azide or prop-2-yn-1-yl carbamate groups. A thermoresponsive copolymers were obtained with the value of cloud point temperature (T_CP) dependent on the type and number of functional groups in the copolymer and on the concentration of solutions. For P(D-co-A) copolymers, the T_CP increased with increasing content of 2-aminoethyl methacrylate comonomer. The presence of azide and prop-2-yn-1-yl carbamate groups caused the changes of T_CP of modified copolymers. All studied copolymers in dilute aqueous solutions aggregated above T_CP to nanoparticles with sizes dependent on the solution concentration, heating procedures, and types and numbers of functional groups present in a copolymer chain. The presence of hydrophilic elements in the chain and the increase in the copolymer concentration led to the enlargement of the particle sizes. Aggregates were crosslinked using click reaction between an azide and prop-2-yn-1-yl carbamate groups that led to stable thermoresponsive nanogels. A systematic study of the behavior of copolymers allowed the determination of the chains useful for possible application in drug delivery.

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.

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.