Recently much effort has been devoted to developing drug delivery systems based on macromolecules of three-dimensional structure. In addition to dendrimers which are widely studied, hyperbranched polymers are gaining more and more attention. Among numerous polymeric materials used in drug delivery systems, aliphatic polycarbonates are one of the most interesting ones due to biocompatibility, nontoxic degradation products, and the absence of autocatalytic effect during the degradation process. However, they show poor solubility in supercritical carbon dioxide. This paper describes the synthesis of 5-(4-hydroxybutyl)-1,3-dioxan-2-one and its application for preparation of hyperbranched aliphatic polycarbonates. Linear analogues of the poly(5-(4-hydroxybutyl)-1,3dioxan-2-one) were prepared, too, and the structures were compared by means of 13 C NMR. Ring-opening polymerization of 5-(4-hydroxybutyl)-1,3-dioxan-2-one led to polymers containing solely primary hydroxyl groups which were subsequently reacted with trifluoroacetic anhydride. The phase behavior of fluorinated polymer in supercritical carbon dioxide was explored as a function of concentration and temperature. Modified hyperbranched polycarbonate showed reasonably good solubility in carbon dioxide. It was shown that hyperbranched structure of a polymer facilitate solubility even though the carbonate structural units do not promote solubility in scCO 2 .

The aim of the study is the investigation of the percolation phenomena in some model copolymer systems. Diblock, triblock, random copolymers, and a blend of homopolymers are studied. For this purpose, we developed an idealized model of polymeric systems. The positions of polymer segments are restricted to vertices of a simple cubic lattice. The chains are at good solvent conditions – the excluded volume is the only interaction between the segments of the chain. The properties of the model chains are determined by means of Monte Carlo simulations with a sampling algorithm based on chain's local changes of conformation. The differences and similarities in the percolation behavior are shown and discussed. The percolation threshold is found to be very weakly dependent on the chain length, however, it appears that the main factor that influenced the percolation threshold is the screening effect of other parts of chains.

Multi-arm star poly(L-lactide) (PLLA) was synthesized in bulk, via ring-opening polymerization of L-lactide initiated by: trimethylolpropane, pentaerythritol, dipentaerythritol, myo-inositol and hyperbranched polyglycerols. The synthesis was carried out on a laboratory scale and also in a model research installation equipped with a 2 L polymerization reactor. Matrix-assisted laser desorption ionization time-of-flight analysis of the products synthesized in the presence of simple polyols and tin 2-ethylhexanoate revealed that the reactions were not entirely selective and the final products were a mixture of multi-arm star, linear and cyclic PLLA. The reactions co-initiated by polyglycerols (PGs) led to polymer mixtures with molar masses in the range 13.5-102 kg mol −1 and intrinsic viscosity significantly lower than that of linear PLLA with the same molar mass. In order to obtain more hydrophobic PG initiator, a suitable method of modification of PG structure was developed. The PG and modified PG branching agents were used to prepare multi-arm star PLLA in the model semi-technical installation. Molar masses of the resulting polymers were in the range 169-249 kg mol −1 and exhibited much lower intrinsic viscosity than the linear homologue. The rheological properties of synthesized materials with commercial PLLA blends as well as thermal and mechanical properties were analysed.

Hyperbranched polymers (HBPs) have been known and extensively investigated for over two decades. However, there are still areas that need to be explored. Recently, much effort has been placed in developing drug delivery systems based on macromolecules of three-dimensional structure. This paper describes the synthesis of random hyperbranched copolyesters of 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) and ε-caprolactone (ε-CL) and their phase behavior in supercritical carbon dioxide (scCO 2 ) after modification with fluorinated anhydrides or chlorotrimethylsilane. The structure of the copolyesters was investigated by means of 1 H and 13 C NMR, FTIR spectroscopies, and MALDI-TOF spectrometry. The influence of the content of chain extender units of 6-hydroxyhexanoic acid (formed from ε-CL) and terminal group functionalities on the solubility of hyperbranched polymers was investigated. The phase behavior of the polymers in supercritical carbon dioxide was explored as a function of concentration and temperature. It was shown that introduction of small amounts (5−10%) of chain extender units into the dense structure of branched poly(bis-MPA) facilitates solubility of a polymer in scCO 2 . Viscosity and contact angle measurements were performed for the synthesized polymers.