Melania Bednarek

Branched polyether with multiple primary hydroxyl groups: polymerization of 3-ethyl-3-hydroxymethyloxetane

Cationic polymerization of 3-ethyl-3-hydroxymethyloxetane gives branched, soluble macromolecules with multiple glycolic end groups. There are approximately 3–4 “normal” units per one branched unit.

Studies of atom transfer radical polymerization (ATRP) of acrylates by MALDI TOF mass spectrometry

Atom transfer radical polymerization (ATRP) of methyl, butyl and tert-butyl acrylates was studied at conditions when low molecular weight polymers (M n ≅ 2 . 10 3 ) are formed, i.e., at relatively high concentration of initiator (ethyl 2-bromopropionate) and calatyst (CuBr/amine). MALDI TOF analysis of the polymer samples isolated at different stages of polymerization revealed that in the course of polymerization potentially active macromolecules terminated with bromine are gradually converted into inactive macromolecules devoid of terminal bromine. A possible transfer mechanism, involving amine is a component of the catalytic system, is proposed. It was shown that quantitative analysis of the MALDI TOF spectra allows one to estimate the ratio of apparent rate constants of propagation and degradative transfer, providing quantitative information to what extent the system conforms to the controlled polymerization scheme.

Synthesis of block copolymers by atom transfer radical polymerization of tert‐butyl acrylate with poly(oxyethylene) macroinitiators

Poly(oxyethylene)s terminated at both ends with 2-bromopropionate end-groups were prepared and characterized by means of MALDI TOF mass spectrometry. It was shown, that atom transfer radical polymerization (ATRP) of methyl methacrylate with a poly(oxyethylene) macroinitiator in bulk proceeds with low initiation efficiency while polymerization of tert-butyl acrylate proceeds with practically quantitative initiation, leading to ABA block copolymers. Originally formed tert-butyl acrylate blocks contain terminal bromine, as expected for the ATRP mechanism. MALDI TOF analysis indicates, however, that in the later stages of polymerization side reactions lead to elimination of terminal bromine.

Cationic copolymerization of tetrahydrofuran with ethylene oxide in the presence of diols: Composition, microstructure, and properties of copolymers

Cationic copolymerization of tetrahydrofuran (THF) with ethylene oxide (EO) in the presence of diols leads to dihydroxy terminated telechelic copolymers. In the present article the influence of copolymerization conditions on the copolymer structure was studied in view of conclusions derived from studies of copolymerization kinetics and mechanism. It was shown that according to established copolymerization mechanism, the number average molecular weights increase linearly with conversion up to M n ≅ 2500, hydroxyl end groups are bound exclusively to EO units and copolymers are composed of [EO]-[THF] y segments. Microstructure of copolymers may be to some extent regulated by changing reaction conditions. Some physical properties of copolymers also were studied.

Aggregation of polylactide with carboxyl groups at one chain end in the presence of metal cations

Polylactides with one or more carboxyl groups at one chain end were synthesized by cationic polymerization according to activated monomer mechanism and by application of “thiol-yne” click chemistry for subsequent functionalization. End groups of such obtained polylactides were converted into ionic groups by neutralization of polymer solutions with metal oxides, mainly calcium oxide, and the aggregation of individual stereoisomers as well as that of the mixture of poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) was investigated. The extent and progress of the aggregation was followed by viscosity measurements, and aggregated polymers in the solid state were examined by SEM and DSC. Solution viscosity increase was observed upon the aggregation of individual PLA stereoisomers, whereas PLA stereocomplex precipitation occurred in the case of the aggregation of PLLA/PDLA/metal oxide mixture.

Ring‐opening polymerization processes involving activated monomer mechanism. Cationic polymerization of cyclic ethers containing hydroxyl groups.

Cationic polymerization of cyclic ethers containing hydroxyl groups as substituents is discussed in terms of contribution of Active Chain End (ACE) and Activated Monomer (AM) polymerization mechanisms.

Polymerization of hydroxymethyloxetanes – synthesis of branched polyethers with primary hydroxyl groups

Oxetanes containing hydroxyl groups can conveniently be prepared using commercially available trimethylolpropane or penthaerithritol. The corresponding monomers, such as 3-ethyl-3-hydroxymethyloxetane (EOX) have been polymerized cationically and it has been shown, that resulting polymers are branched. These polymers are of particular interest, since in contrast to some other polyhydroxyethers (like polyglycidol) all of the hydroxyl groups are primary ones. Moreover, all of the -CH 2 OH groups are attached to the quaternary carbon atoms. These features are rather unique and may be advantageous from the point of view of possible applications.

Mechanism of cyclics formation in the cationic copolymerization of tetrahydrofuran with ethylene oxide in the presence of diols

Cationic copolymerization of ethylene oxide (EO) with tetrahydrofuran (THF) in the presence of diols leads to the formation of hydroxytelechelic copolymers. The process combines the features of an activated monomer mechanism (secondary oxonium ions as active species) with those of an active chain end mechanism (tertiary oxonium ions as active species). Due to the participation of tertiary oxonium ions, back-biting leads to the formation of cyclic oligomers. The effect of reaction conditions on the content of the cyclic fraction was studied, the individual cyclic oligomers were identified, and the results are interpreted in terms of a reaction mechanism.

Modification of hydrolytic stability of high molecular weight poly(e-caprolactone) by addition of medium molecular weight poly(e-caprolactone) aggregated in the presence of CaO

Medium molecular weight poly( -caprolactone) containing three carboxyl groups at one chain end (PCL5000) and the same polymer but aggregated in the presence of CaO (PCL5000/CaO) were used as an additive for modification of hydrolytic stability of high molecular weight poly( -caprolactone) (PCL80000). Thermal and mechanical properties of PCL80000 and its composites together with their molecular weight changes upon hydrolysis were investigated. The composite obtained using PCL5000/CaO showed higher tendency to hydrolytic degradation than unmodified PCL80000 with the preservation of mechanical properties.