Jan Libiszowski

Block and random copolymers of ε-caprolactone

Abstract Conditions of the living homopolymerization of e-caprolactone (CL), lactides (LA), and of the homo-oligomerization of γ-butyrolactone (BL) are briefly described. Then block and random copolymerizations of CL with LA are shortly reviewed. The microstructure of the resulting copolyesters in relation to some peculiarities of these processes is discussed in more detail. It is also shown that the otherwise ‘non-polymerizable’ BL does form high molecular weight copolymers with CL, containing up to 50 mol% repeating units derived from BL. Their molecular weight is controlled by the concentrations of the consumed comonomers and the starting concentration of the initiator. NMR and DSC data indicate the random structure of copolymers. TGA traces of the BL/CL copolymers show that the presence of the γ-oxybutyryl repeating units randomly distributed within the poly(CL) chains improves the thermal stability of the latter.

On the mechanism of polymerization of cyclic esters induced by tin(II) octoate

Mechanism of initiation and propagation in polymerization of ϵ-caprolactone and L,L-dilactide induced with tin(II) octoate (Sn(Oct)2) and Sn(Oct)2/n-butyl alcohol system is presented. Tin(II) alkoxide bond formation is required in reaction of Sn(Oct)2 with hydroxyl group containing compound to form a true initiator. Then tin(II) alkoxide end group is an active centre in the further propagation.

Kinetics and mechanism of cyclic esters polymerization initiated with covalent metal carboxylates, 5. End-group studies in the model ε-caprolactone and L, L-dilactide/tin(II) and zinc octoate/butyl alcohol systems

Ring-opening polymerizations of e-caprolactone (CL) and L,L-dilactide (LA) initiated by tin(II) octoate (Sn(Oct)2) and zinc octoate (Zn(Oct)2) and co-initiated with butyl alcohol (BuOH) carried out in tetrahydrofuran as a solvent at 80 °C were studied. By means of MALDI-TOF mass spectrometry, the formation of several populations of polyester macromolecules bearing various end-groups was revealed, namely for poly(e-caprolactone) (PCL): BuO(O)CPCLOH (A), BuO(O)CPCLOct (B), HO(O)CPCLOH (C), HO(O)CPCLOct (D), and PCL cyclics (E), and for poly(L-lactide) (PLA): BuO(O)CPLAOH (A′), BuO(O)CPLAOct (B′), HO(O)CPLAOH (C′), and HO(O)CPLAOct (D′) (where Bu = C4H9 and Oct = O(O)CCH(C2H5)C4H9). In these polymerizations the end-groups in the originally formed macromolecules change slowly with time. In the LA/Sn(Oct)2/BuOH system at the beginning of polymerization almost exclusively macromolecules of the structure A′ are formed and then structures B′, C′, and D′ start to appear, however, after a period more than 300 times (at 80 °C) longer than that required for full monomer conversion, these macromolecules give exclusively esterified B′ and D′ chains. With Zn(Oct)2/BuOH all of these processes are much slower and less selective. Dependencies of mass fraction of macromolecules with various end-groups on time in L,L-dilactide polymerization initiated with Sn(Oct)2/BuOH system. Symbols ▵, ▴, ○, • correspond to PLA populations A′, B′, C′, and D′.

Complementarity of solvent-free MALDI TOF and solid-state NMR spectroscopy in spectral analysis of polylactides.

We report systematic studies of solvent-free modification of matrix-assisted laser desorption/ionization time-of-flight (SF MALDI-TOF) mass spectrometry in analysis of synthetic polymers employing solid-state NMR spectroscopy as a supporting technique. In the present work oligomeric (M(n) = 4000 g mol(-1)) poly(L-lactide) (PLLA) was employed as a reference sample. The analyte was embedded into four matrixes commonly used in MALDI-TOF analysis of polymers: 1,8-dihydroxy-9-anthracenone (DT), 2,5-dihydroxybenzoic acid (DHB), 2-(4 hydroxyphenylazo)-benzoic acid (HABA), and trans-3-indoleacrylic acid (IAA). Solid-state NMR measurements clearly showed that the initial crystallinity of PLLA had no influence on quality of SF MALDI-TOF spectra since the crystalline structure of the analyte was not preserved during analyte/matrix grinding. Interestingly, the matrix remained crystalline during the samples preparation. It was also found that, on the contrary to the dried droplet (DD) method, the SF approach leads to highly resolved mass spectra for a large variety of matrixes. Finally, problems of polymorphism and mechanochemical processes that can occur during the analyte/matrix grinding are briefly discussed.

Application of ionic liquid matrices in spectral analysis of poly(lactide) - solid state NMR spectroscopy versus matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry

The work presented here shows the complementarity of Solid State NMR (SS NMR) spectroscopy and Matrix-Assisted Laser Desorption/Ionization-time-of-flight (MALDI-TOF) mass spectrometry in spectral analysis of poly(L-lactide) (PLLA) using second-generation ionic liquid matrices (ILM II) prepared from N,N-diisopropylethylamine (DEA) and DHB (2,5-dihydroxybenzoic acid), IAA (3-indoleacrylic acid), and HABA (2-(4-hydroxyphenylazo) benzoic acid). The 13C cross-polarization (CP) magic angle spinning (CP/MAS) SS NMR technique was used to study the structure of ionic liquid matrices, their thermal stability, and the influence of ILM on the morphology of polymer. A comparison of MALDI-TOF spectra for samples prepared employing the dried droplet (DD) and the solvent free (SF) mode showed that the former approach gave better results (signal to noise ratio) very likely due to intimate contact between analyte and matrix domains. This hypothesis was verified by analysis of CP build-up curves for DHB–DEA–PLLA samples prepared employing both methods. We also showed that an alternative method of sample preparation based on the melting of ILM II together with a suspended polymer in the liquid matrix is unsatisfactory, particularly for those matrices which can undergo isomerization at higher temperatures (e.g., HABA–DEA and IAA–DEA).

KINETICS OF ELEMENTARY REACTIONS IN CYCLIC ESTER POLYMERIZATION

Kinetics of the polymerization of L-lactide (LA) and e-caprolactone (CL) initiated with dialkylaluminum alkoxide, aluminum trialkoxide and related metal alkoxides is reviewed. The former give aggregating active species, and a method is described allowing simultaneous determination of the rate constants of propagation and aggregation equilibrium constants. It has been shown that tin“ dicarboxylate (dioctoate) requires a coinitiator in order to start polymerization. Both kinetic and spectroscopic evidence indicate that propagation proceeds on the —Sn-OR bonds. The major reaction accompanying propagation is the chain transfer-to polymer; either inter or intramolecular. Methods are described giving access to the rate constants of both transfers Finally, correlation is given between the atomic number of metal involved in the active species and the determined rate constants: the larger the atomic number, the higher is the rate constant of propagation and the less selective is the polymerization process.

Copolymers of 7‐oxabicyclo[2.2.1] heptane with 1,3‐dioxane and promesogenic telechelic oligomers thereof

Copolymers of 7-oxabicyclo[2.2.1 heptane (B) ( and of its 2-methyl derivatives) with 1,3-dioxane (D) were obtained by cationic copolymerization initiated with benzoylium hexafluoroantimonate. Structure of copolymers was determined by 1 H- and 13 C-NMR. The proportion of the acetal bonds in copolymers was additionally confirmed in studies of the products of hydrolysis (only the acetal bonds hydrolyze). D is unable to homopolymerize for the thermodynamic reasons and therefore mostly pseudoperiodic copolymers (-DB x -) y are formed. Nevertheless, the reshuffling reactions are responsible for the appearance of wrong units. These are: the separate oxymethylene and oxy-1,3-propylene units (P, subunits of D) located between two B units. Only the acetal bonds are cleaved in the acidic hydrolysis with dilute HCI. This gives the promesogenic telechelic oligomers of mostly HO-P-B x -OH structure. This article is the first to describe successful cationic copolymerization of cyclic acetal with a cyclic ether. Moreover, the inability of D to homopolymerize gives the thermodynamic basis of the pseudoperiodic copolymer formation.