Michał Sobota

Study of Aliphatic-Aromatic Copolyester Degradation in Sandy Soil and Its Ecotoxicological Impact

Degradation of poly[(1,4-butylene terephthalate)-co-(1,4-butylene adipate)] (Ecoflex, BTA) monofilaments (rods) in standardized sandy soil was investigated. Changes in the microstructure and chemical composition distribution of the degraded BTA samples were evaluated and changes in the pH and salinity of postdegradation soil, as well as the soil phytotoxicity impact of the degradation products, are reported. A macroscopic and microscopic evaluation of the surface of BTA rod samples after specified periods of incubation in standardized soil indicated erosion of the surface of BTA rods starting from the fourth month of their incubation, with almost total disintegration of the incubated BTA material observed after 22 months. However, the weight loss after this period of time was about 50% and only a minor change in the M(w) of the investigated BTA samples was observed, along with a slight increase in the dispersity (from an initial 2.75 up to 4.00 after 22 months of sample incubation). The multidetector SEC and ESI-MS analysis indicated retention of aromatic chain fragments in the low molar mass fraction of the incubated sample. Phytotoxicity studies revealed no visible damage, such as necrosis and chlorosis, or other inhibitory effects, in the following plants: radish, cres, and monocotyledonous oat, indicating that the degradation products of the investigated BTA copolyester are harmless to the tested plants.

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.

Forensic Engineering of Advanced Polymeric Materials. Part 1 –Degradation Studies of Polylactide Blends with Atactic Poly[(R,S)-3-hydroxybutyrate] in Paraffin

Classical forensic polymer engineering concerns a study of failure in polymer products. This area of science comprises fracture of plastic products, or any other reason why such a product fails in service, or fails to meet its specification.1 So far, most of the reported case studies concern ex-post investigations of traditional polymeric materials such as PE, PP, PS, PVC, ABS or their thermoplastic composites. Little is known about forensic engineering of novel and advanced polymeric materials. Thus, there is a real gap in this area of knowledge. Furthermore, the ex-ante studies are needed to define and minimise the potential failure of novel polymer products before specific applications. Environmental stress cracking (ESC) is one of the most common causes of unexpected brittle failure of thermoplastic (especially amorphous) polymers. The rate of ESC is dependent on many factors, including, for example, the polymer’s chemical composition, bonding, crystallinity, surface roughness, molar mass and residual stress. It also depends on the chemical nature of liquid media and the temperature of the system. Thus, evaluation and understanding of the structure, properties and behaviour of advanced polymer materials for perspective practical applications is needed, especially in the field of compostable polymer packages of long-life products, such as cosmetics or household chemicals. Because of the slow environmental degradation of traditional packaging, the use of conventional plastics is accompanied by significant ecological problems. To reduce plastic waste from the packaging industry, biodegradable polymers have become interesting alternatives, for packages with a long shelf life.2 The most important environmentally friendly plastics are generally based on aliphatic polyesters, such as poly(lactic acid), poly(3-hyForensic Engineering of Advanced Polymeric Materials. Part 1 – Degradation Studies of Polylactide Blends with Atactic Poly[(R,S)-3-hydroxybutyrate] in Paraffin

Star-shaped azomethines based on tris(2-aminoethyl)amine. Characterization, thermal and optical study.

The synthesis and detailed (physico)-chemical ((1)H/(13)C NMR, FTIR, UV-vis and elemental analysis) characterizations of new star-shaped compounds based on tris(2-aminoethyl)amine, including in their structure an azomethine function (HCN-) and alkoxysemiperfluorinated (-O-(CH(2))(3)-(CF(2))(7)-CF(3)), octadecyloxy aliphatic (-O-(CH(2))(17)-CH(3)) chain or two phenyl rings (-Ph-Ph-) as a terminal group, were reported. The mesomorphic behavior was investigated by means of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and additionally by FTIR(T) and UV-vis(T) spectroscopy. Wide-angle X-ray diffraction (WAXD) technique was used to probe the structural properties of the azomethines. Moreover, the azomethine A1 was electro-spun to prepare fibers with poly(methyl methacrylate) (PMMA) and investigated by DSC and POM. Additionally, a film of the A1 with PMMA was cast from chloroform and the thermal properties of the film were compared with the thermal properties of the fiber and powder. It was showed that terminal groups dramatically influence the thermal and optical properties of the star-shaped azomethines.

Bio)degradation studies of degradable polymer composites with jute in different environments

The introduction of new, environmentally friendly and sustainable plastics in the packaging and end-user industry is a solution to the problem of waste management. The degradation of polyesters in different environments could result from an enzymatic attack or simple hydrolysis, or both. The degree of degradation of blends containing polylactide and poly(3-hydroxybutyrate-co-4-hydroxybutyrate), PLA/P(3HB-co-4HB), and its composites with 20 %wt of jute incubated in distilled water at 70 ℃ (abiotic conditions) under industrial composting conditions (system KNEER) was investigated using a Zeiss optical microscope, an atomic force microscope, gel permeation chromatography, differential scanning calorimetry and thermal gravimetric analysis. PLA/P(3HB-co-4HB) was tested under laboratory composting conditions in order to verify whether biodegradation of this material occurs under industrial composting conditions. The addition of jute fibres did significantly reduce the disintegration of the composites during degradation.

Human procollagen type I surface-modified PHB-based non-woven textile scaffolds for cell growth: preparation and short-term biological tests

3D fine porous structures obtained by electrospinning a poly[(R,S)-3-hydroxybutyrate] (aPHB)/ poly[(R)-3-hydroxybutyrate] (PHB) (85/15 w/w) blend were successfully modified with human procollagen type I by simple immersion of the polyester scaffold in an aqueous solution of the protein. Effective modification of the scaffold with human procollagen I was confirmed by an immunodetection test, which revealed the presence of the procollagen type I as an outer layer even on inner structures of the porous matrixes. Biological tests of 3D fabrics made of the PHB blend provide support for the adhesion and proliferation of human fibroblasts, while their modification with procollagen type I increased the biocompatibility of the final scaffolds significantly, as shown by the notable increase in the number of attached cells during the early hours of their incubation. Based on these findings, human procollagen type I surface-modified aPHB/PHB scaffolds should be considered a promising material in regenerative medicine.

Crystallinity as a tunable switch of poly(L-lactide) shape memory effects

Materials with shape memory effect (SME) have already been widely used in the medical field. The interesting part of this group is represented by double function materials. The bioresorption and SME ability are common in polyesters implants. The first information about vascular stent made of bioresorbable polyester with SME was published in 2000. However, there are not many investigations about SME control of elements in the aspect of material processing. In the present work, the ability to control the shape memory (SM) of bioresorbable and semicrystalline poly(L-lactide) (PLLA) is investigated. The studies are based on the unexpected effect of material orientation which was demonstrated even at low percentage deformation in crystallized mould injected material. The presented studies revealed that the different degrees of crystallinity obtained during processing might be a useful switch to create a tailored SME for a specific application. The prepared samples of variable morphology revealed a possibility to control the value of material stress during permanent shape recovery. The degree of shape recovery of the prepared samples was also controlable. The highest stress value observed during permanent shape recovery reached 10MPa for the sample annealed 60min at 115°C even when the sample was only deformed in 8%. The other significant aspect of this work is to present the problem of slow crystallization of the material during and after processing (cooling rate) as well as the possibility of negative SME change during the shelf life of the fabric.

Application of the melt-blown technique in the production of shape-memory nonwoven fabrics from a blend of poly(L-lactide) and atactic poly[(R,S)-3-hydroxy butyrate]:

Shape-memory materials have recently gained significant attention from scientists and industries around the world. Their useful properties and ability to change their shape when triggered by different stimuli have encouraged researchers to develop this area of science. The examinations conducted herein concern a nonwoven material with thermally induced shape-memory properties, produced by the melt-blown technique. The subject of the research was a nonwoven fabric made from biodegradable poly(L-lactide) (PLLA) blended with atactic polyhydroxybutyrate (a-PHB). The main aim of the presented research was to determine the technological parameters of the melt-blown process and investigate the shape fixing and recovery mechanisms in the obtained material. Thermal, mechanical, and structural analyses were conducted to describe the properties of the smart fabric. The results obtained for the nonwoven fabric produced under specific conditions and selected process parameters showed that it possesses a controllable, thermally induced shape-memory effect. Shape-memory textiles have great potential for diverse applications, in particular in medical science.

The impact of shape memory test on degradation profile of a bioresorbable polymer

The semicrystalline poly(L-lactide) (PLLA) belongs to the materials with shape memory effect (SME) and as a bioresorbable and biocompatible polymer it have found many applications in medical and pharmaceutical field. Assessment of the SME impact on the polymer degradation profile plays crucial role in applications such as drug release systems or in regenerative medicine. Herein, the results of in vitro degradation studies of PLLA samples after SME full test cycle are presented. The samples were loaded and deformed in two manners: progressive and non-progressive. The performed experiments illustrate also influence of the material mechanical damages, caused e.g. during incorrect implantation of PLLA product, on hydrolytic degradation profile. Apparently, degradation profiles are significantly different for the material which was not subjected to the deformation and the deformed ones. The materials after deformation of 50% (in SME cycle) was characterized by non-reversible morphology changes. The effect was observed in deformed samples during the SME test which were carried out ten times.

Formulation of delivery systems with risperidone based on biodegradable terpolymers

ABSTRACT Risperidone is applied in oral dosage formulations in the treatment of mental diseases. Current trends point toward parenteral delivery systems based on poly(lactide‐co‐glycolide), with wafers or rods being the more attractive option than the routinely used intramuscular suspension with microparticles. The aim of our work was to study the utility of solution casting and hot melt extrusion in the formulation of wafers and rods with risperidone based on terpolymers, namely poly(lactide‐co‐glycolide‐co‐trimethylene carbonate) and poly(lactide‐co‐glycolide‐co‐&egr;‐caprolactone). Synthesis of the terpolymers was carried out by using a non‐toxic zirconium initiator and a racemic (LL/DD) or optically active form of the lactide monomer. The delivery systems were analyzed by NMR, DSC, GPC, and SEM. The release profile was monitored by HPLC. Terpolymer chain microstructure, glass transition temperature, and morphology revealed unchanged values after formulation. Solution casting resulted in a drop in molecular weight to a smaller degree than hot melt extrusion. The presence of risperidone influenced another decrease in molecular weight. Both methods are adequate for the formulation of delivery systems based on terpolymers for prolonged release of risperidone. An adequate selection of monomer composition in terpolymers allows to control the release period. Risperidone was released in three phases, however, the burst effect was observed for poly(L‐lactide‐co‐glycolide‐co‐&egr;‐caprolactone).