Henryk Janeczek

Copolymerization of glycolide andε-caprolactone, 2. Random copolymerization in the presence of tin octoate

The copolymerization of glycolide with e-caprolactone was performed in the presence of tin octoate at moderate temperatures (100 and 150°C). The influence of the conditions (comonomer ratio, temperature) on the chain microstructure of the obtained copolymers was examined. Transesterification was found to affect considerably the course of the process. The effect of copolymer composition and chain microstructure on thermal properties was also investigated. A phase separation of glycolidyl and caproyl microblocks was observed. The heat of melting of the crystalline phases was found to be dependent on the length of glycolidyl and caproyl microblocks.

(Photo)physical Properties of New Molecular Glasses End-Capped with Thiophene Rings Composed of Diimide and Imine Units

New symmetrical arylene bisimide derivatives formed by using electron-donating–electron-accepting systems were synthesized. They consist of a phthalic diimide or naphthalenediimide core and imine linkages and are end-capped with thiophene, bithiophene, and (ethylenedioxy)thiophene units. Moreover, polymers were obtained from a new diamine, N,N′-bis(5-aminonaphthalenyl)naphthalene-1,4,5,8-dicarboximide and 2,5-thiophenedicarboxaldehyde or 2,2′-bithiophene-5,5′-dicarboxaldehyde. The prepared azomethine diimides exhibited glass-forming properties. The obtained compounds emitted blue light with the emission maximum at 470 nm. The value of the absorption coefficient was determined as a function of the photon energy using spectroscopic ellipsometry. All compounds are electrochemically active and undergo reversible electrochemical reduction and irreversible oxidation processes as was found in cyclic voltammetry and differential pulse voltammetry (DPV) studies. They exhibited a low electrochemically (DPV) calculated energy band gap (Eg) from 1.14 to 1.70 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital levels and Eg were additionally calculated theoretically by density functional theory at the B3LYP/6-31G(d,p) level. The photovoltaic properties of two model compounds as the active layer in organic solar cells in the configuration indium tin oxide/poly(3,4-(ethylenedioxy)thiophene):poly(styrenesulfonate)/active layer/Al under an illumination of 1.3 mW/cm2 were studied. The device comprising poly(3-hexylthiophene) with the compound end-capped with bithiophene rings showed the highest value of Voc (above 1 V). The conversion efficiency of the fabricated solar cell was in the range of 0.69–0.90%.

Synthesis of block copolymers of ε-caprolactone and lactide in the presence of lithium t-butoxide

SummaryHigh molecular mass copolymers with microphase separation can be obtained in block copolymerization of ε-caprolactone with L,L- and D,L-lactide carried out in the presence of lithium t-butoxide. A kind of solvent applied strongly affects the molecular mass and polydispersity index of obtained copolymers.

Liquid-induced crystallization of a bisphenol-A polycarbonate

Abstract The liquid-induced crystallization of bisphenol-A polycarbonate films in the presence of CCl4 and acetone as swelling agents has been investigated by means of differential microcalorimetry and differential scanning calorimetry (d.s.c.). Results of microcalorimetric measurements were used to obtain thermokinetic curves and to determine heat effects in the liquid-induced crystallization process. Results of calorimetric measurements were subjected to Avrami analysis. The d.s.c. experiments revealed a maximum crystallinity of about 17% in the case of samples swollen in CCl4 and 20% for those swollen in acetone.

Forensic engineering of advanced polymeric materials. Part III - Biodegradation of thermoformed rigid PLA packaging under industrial composting conditions

This paper presents a forensic engineering study on the biodegradation behaviour of prototype packaging thermoformed from PLA-extruded film and plain PLA film under industrial composting conditions. Hydrolytic degradation in water was conducted for reference. The effects of composting duration on changes in molar mass, glass transition temperature and degree of crystallinity of the polymeric material were monitored using gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The chemical structure of water soluble degradation products of the polymeric material was determined using nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS). The results show that the biodegradation process is less dependent on the thermoforming process of PLA and more dependent on the composting/degradation conditions that are applied. The increase in the dispersity index, leading to the bimodal molar mass distribution profile, suggests an autocatalytic hydrolysis effect at the early stage of the composting process, during which the bulk hydrolysis mechanism dominantly operates. Both the prototype PLA-packaging and PLA rigid film samples were shown to have a gradual increase in opacity due to an increase in the degree of crystallinity.

Characterisation and mesomorphic behaviour of new aliphatic–aromatic azomethines containing ester groups

Two series of novel symmetrical azomethines prepared by the condensation of 4,4′-(butane-1,4-diylbis(oxy))bis(butane-4,1-diyl)bis(4-aminobenzoate) (PBBA470) and 5,10,15,20,25,30,35,40,45,50,55,60-dodecaoxatetrahexacontane-1,64-diylbis(4-aminobenzoate) (PBBA 1200) with a range of aldehydes have been characterised by 1H and 13C nuclear magnetic resonance, Fourier transform infrared and UV–Vis spectroscopy. Current–voltage measurements were performed using a device comprising indium–tin oxide/compound/Alq3/Al. The effect of rod length and the nature of the terminal chains on the thermal and mesomorphic behaviour of these materials were investigated by differential scanning calorimetry, polarising optical microscopy and wide- and small-angle X-ray diffraction. Additionally, the compounds were studied using various atomic force microscopy techniques, including mode and phase imaging, and measurements based on local contrast force–distance curves and roughness, together with skew and kurtosis, are presented.

Characterization, optical and thermal properties of new azomethines based on heptadecafluoroundecyloxy benzaldehyde

New thermotropic liquid crystals containing a long alkoxysemiperfluorinated chain (-O-(CH2)3-(CF2)7-CF3), one linking unit in mesogenic cores (HC=N-) and different functional end-groups such as 4-hexadecyl-, 4-n-hexadecyloxy- chain, or biphenyl-4-carbonitrile, 4-diazenyl-N,N-dimethylbenzene or pyren were synthesized via a one-step route. The methods of nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), ultraviolet–visual (UV-vis) and photoluminescence (PL) spectroscopy as well as differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) were used. The absorption (UV-vis) and PL features of all compounds are documented. The amine had an effect on the mesomorphic properties of the azomethines. An enantiotropic smectic phase was observed for all of the systems studied. As a result of DSC and POM investigations, it is shown that liquid crystalline properties of the azomethines exhibit a strong dependence of the end-groups. The mesomorphic behaviour of the compounds was investigated also by FTIR(T) and UV-vis(T) spectroscopy. Current–voltage measurements were performed on an ITO/compound/Alq3/Al device.

Bioresorbable terpolymers based on L-lactide, glycolide and trimethylene carbonate with shape memory behaviour

This paper presents the course of synthesis and the properties of biodegradable terpolymers obtained by ROP of L-lactide with glycolide, catalysed with zirconium(IV) acetylacetonate and conducted in the presence of a macroinitiator – trimethylene carbonate oligomers terminated with hydroxyl groups. The oligomers were also prepared by ROP reaction of TMC catalysed by zinc(II) acetylacetonate monohydrate in the presence of polyols as initiators. Depending on the type of initiator used, the oligomers had a linear or branched structure of the chain with different hydroxyl end-groups. Some of the obtained oligomers formed a network. The effect of the terpolymer chain structure on mechanical and thermomechanical properties as well as shape-memory behaviour was shown. The ability to control the speed of return from a temporary to a permanent shape, the value of stress of return triggered by this phenomenon, and the magnitude of the temperature range in which the phenomenon took place through appropriate selection of conditions for programming the temporary shape or/and terpolymer chain microstructure has been shown. The possibility of adjusting these parameters as presented in this paper is vital in the process of designing a bioresorbable material, which can be used for forming self-expanding stents or self-clamping surgical staples.

Thermal and current–voltage behaviour of liquid crystal compounds with rod and bent shapes comprising alkoxysemifluorinated and imine segments

The synthesis and mesomorphic properties of a series of thermotropic liquid crystalline symmetrical rod and bent-shaped imines containing two long alkoxysemifluorinated chains were reported. Three different diamines varying in the number of phenylene rings from 1 to 3 were used to understand structure–mesomorphic property correlation. Differential scanning calorimetry, X-ray diffraction and polarised optical microscopy were used to determine their phase transition behaviour. An enantiotropic smectic phase was observed for all the systems studied. The thermal properties of the azomethines were discussed in relation to the core shape and length of the core. Current–voltage measurements were performed on ITO/compound/Alq3/Al and ITO/TiO2/compound/Alq3/Al devices before and after irradiation with light (about 1000 W m−2). To prepare the TiO2 layer, the sol-gel technique was applied.

Mesomorphic Behavior of Symmetrical and Unsymmetrical Azomethines with Two Imine Groups

Seven symmetrical azomethines with two imine groups (HC=N) were synthesized by condensation of the benzene-1,4-dicarboxaldehyde with five amines (first group: A1-A5) and of the 2,5-thiophenedicarboxaldehyde with two amines (second group: AT1-AT2). Additionally, two unsymmetrical azomethines were obtained by a two step condensation of benzene-1,4-dicarboxaldehyde with pyren-1-amine (1st step) (abbreviated hereinafter as AP1) and then AP1 was reacted with 4-dodecylaniline or 4-hexadecylaniline (2nd step) (third group: AP1A-AP1B). Liquid crystalline properties of the azomethines were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and UV-vis spectroscopy in the function of temperature [UV-vis(T)]. The Wide-Angle X-ray Diffraction (WAXD) technique was used to probe the structural properties of the azomethines. Mesomorphic behavior was observed for symmetrical and unsymmetrical azomethines, obtained from the benzene-1,4-dicarboxaldehyde and symmetrical ones prepared from 2,5-thiophenedicarboxaldehyde and different amines having aliphatic chains. Based on the POM and DSC measurements the following mesophases were detected: nematic, smectic A, smectic C, smectic F (I), smectic G (J).