Biopolymer Compositions Based on Poly(3-hydroxybutyrate) and Linear Polyurethanes with Aromatic Rings-Preparation and Properties Evaluation.

Polymer biocompositions of poly(3-hydroxybutyrate) (P3HB) and linear polyurethanes (PU) with aromatic rings were produced by melt-blending at different P3HB/PU weight ratios (100/0, 95/5, 90/10, and 85/15). Polyurethanes have been prepared with 4,4'-diphenylmethane diisocyanate and polyethylene glycols with molar masses of 400 g/mol (PU400), 1000g/mol (PU1000), and 1500 g/mol (PU1500). The compatibility and morphology of the obtained polymer blends were determined by infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The effect of the polyurethane content in the biocompositions on their thermal stability and mechanical properties was investigated and compared with those of the native P3HB. It was shown that increasing the PU content in P3HB-PU compositions to 10 wt.% leads to an improvement in the mentioned properties. The obtained results demonstrated that the thermal stability and mechanical properties of P3HB were improved, particularly in terms of increasing the degradation temperature, reducing hardness, and increasing impact strength. The best thermal and mechanical properties were shown by the P3HB-PU polymer compositions containing 10 wt.% of polyurethane modifiers, especially PU1000, which was also confirmed by the morphology analysis of these biocompositions. The presence of polyurethanes in the resulting polymer biocomposites decreases their glass transition temperatures, i.e., makes the materials more flexible. The resulting polymer biocompositions have suitable mechanical properties and thermal properties within the processing conditions for the predicted application as biodegradable, short-lived products for agriculture.

Polymer Biocompositions and Nanobiocomposites Based on P3HB with Polyurethane and Montmorillonite.

Due to the growing interest in biopolymers, biosynthesizable and biodegradable polymers currently occupy a special place. Unfortunately, the properties of native biopolymers make them not good enough for use as substitutes for conventional polymers. Therefore, attempts are being made to modify their properties. In this work, in order to improve the properties of the poly(3-hydroxybutyrate) (P3HB) biopolymer, linear aliphatic polyurethane (PU) based on 1,4-butanediol (BD) and hexamethylene 1,6-diisocyanate (HDI) was used. The conducted studies on the effect of the amount of PU used (5, 10, 15 and 20 m/m%) showed an improvement in the thermal properties of the prepared polymer blends. As part of the tested mechanical properties of the new polymer blends, we noted the desired increase in the tensile strength, and the impact strength showed a decrease in hardness, in particular at the presence of 5 m/m% PU. Therefore, for further improvement, hybrid nanobiocomposites with 5 m/m% PU and organically modified montmorillonite (MMT) (Cloisite 30®B) were produced. The nanoadditive was used in a typical amount of 1-3 m/m%. It was found that the obtained nanobiocomposites containing the smallest amount of nanofillers, i.e., 1 m/m% Cloisite®30B, exhibited the best mechanical and thermal properties.

The cytisine-enriched poly(3-hydroxybutyrate) fibers for sustained-release dosage form.

The polymeric cytisine-enriched fibers based on poly(3-hydroxybutyrate) were obtained using electrospinning method. The biocompatibility study, advanced thermal analysis and release of cytisine from the poly(3-hydroxybutyrate) fibers were carried out. The nanofibers' morphology was evaluated by scanning electron microscopy. The formation and description of phases during the thermal processes of fibers by the advanced thermal analysis were examined. The new quantitative thermal analysis of polymeric fibers with cytisine phases based on vibrational, solid and liquid heat capacities was presented. The apparent heat capacity of fibers was measured using the standard differential scanning calorimetry. The quantitative analysis allowed for the study of the glass transition and melting/crystallization process. The mobile amorphous fraction, degree of crystallinity and rigid amorphous fraction were determined depending on the thermal history of semicrystalline polymeric fibers. Furthermore, the cytisine dissolution behaviour was studied. It was observed that the kinetic of the release from polymeric nanofiber is delayed than for the marketed product. The immunosafety of the tested polymeric nanofibers with cytisine was confirmed by the Food and Drug Agency Guidance as well as the European Medicines Agency. The polymeric matrix with cytisine seems to be a promising candidate for the prolonged release formulation.

Tracking of Thermal, Physicochemical, and Biological Parameters of a Long-Term Stored Honey Artificially Adulterated with Sugar Syrups.

The growing phenomenon of honey adulteration prompts the search for simple methods to confirm the authenticity of honey. The aim of the study was to evaluate the changes in thermal characteristics, physicochemical parameters, antioxidant and enzymatic activity of honey subjected to artificial adulteration. Two series of products were prepared with the use of two different sugar syrups with an increasing dosage of adulterant (0 to 30%). After 24 months of storage, the quality of adulterated samples (partially crystallized) was assessed in comparison to the control honey (solid). Used adulteration changed physicochemical parameters and reduced antioxidant and enzymatic activity of honey (p < 0.05). The admixture of syrup and invert (p < 0.05) reduced the viscosity of liquid phase of delaminated honey in a dose-dependent manner. In the study, artificially adulterated honeys were controlled using the standard differential scanning calorimetry, DSC. In all adulterated honeys, a specific glass transition, TG, was observed in the range of 34-38.05 °C, which was not observed for control honey and pure adulterants. Moreover, the additional Tgs were observed in a wide range from -19.5 °C to 4.10 °C for honeys adulterated by syrup only. In turn, the Tg in range of 50.4-57.6 °C was observed only for the honeys adulterated by invert. These specific Tg seem to be useful to detect honey adulteration and to identify the kind of adulterant used.

Heat capacity of cytisine - the drug for smoking cessation.

The characterization of cytisine (CYT) and its blends with poly(lactic acid) was performed using thermal analysis, elemental analysis, infrared spectroscopy, and powder X-ray diffractometry. The heat capacities, total enthalpy, and phase transitions of CYT were established from 1.8 to 448.15 K (-271.35 - 175 °C) by advanced thermal analysis. Data were obtained using a Quantum Design Physical Property Measurement System (PPMS) and a differential scanning calorimetry (DSC). The low-temperature heat capacity of the crystalline CYT in the range of 1.8 to 300 K (-271.35 - 26.86 °C) was measured by PPMS and fitted to a theoretical model in the low temperature region below 11 K (-262.15 °C), to orthogonal polynomials in the middle range 5 K < T < 60 K (-268.15 °C < t < -213.15 °C) and to the Debye and Einstein functions in the high range of temperature above 60 K (-213.15 °C). The liquid heat capacity was calculated based on the approximated linear regression data above the molten state of the experimental heat capacity of CYT obtained by the standard DSC measurements, and it was expressed as Cpliquid = 0.0838T + 346.78 J·K-1·mol-1. The calculated heat capacity in the solid state was extended to a higher temperature and was used, together with liquid heat capacity, as the reference baselines for the advanced thermal analysis of CYT. The PPMS and DSC/TMDSC methods are complementary methods for thermal analysis of cytisine. The PPMS method allowed determination of the equilibrium heat capacity in the solid state, which together with the equilibrium heat capacity in the liquid state allowed to analyze of the experimental apparent heat capacity of cytisine obtained based on DSC. The melting temperature and the total heat of fusion of crystalline material were established as 431.8 K (158.65 °C) and 26.5 kJ·mol-1, respectively. The solid and liquid heat capacities and transition parameters of CYT were applied to calculate total enthalpies for fully amorphous and crystalline states. Analyses of DSC and X-ray confirmed the presence of the solid-solid transition linking with not so far described a polymorphism phenomenon of CYT. Based on the thermogravimetric analysis the temperature of degradation of CYT was determined as 460.5 K (187.35 °C). Also, a preliminary thermal analysis of the blends of cytisine and poly(lactic acid) as a new candidate for drug delivery system was presented.

Polymer/Layered Clay/Polyurethane Nanocomposites: P3HB Hybrid Nanobiocomposites-Preparation and Properties Evaluation.

This paper presents an attempt to improve the properties of poly(3-hydroxybutyrate) (P3HB) using linear aliphatic polyurethane (PU400) and organomodified montmorillonite (MMT)-(Cloisite®30B). The nanostructure of hybrid nanobiocomposites produced by extrusion was analyzed by X-ray diffraction and transmission electron microscopy, and the morphology was analyzed by scanning electron microscopy. In addition, selected mechanical properties and thermal properties were studied by thermogravimetric analysis, TGA, and differential scanning calorimetry, DSC. The interactions of the composite ingredients were indicated by FT IR spectroscopy. The effect of the amount of nanofiller on the properties of prepared hybrid nanobiocomposites was noted. Moreover, the non-equilibrium and equilibrium thermal parameters of nanobiocomposites were established based on their thermal history. Based on equilibrium parameters (i.e., the heat of fusion for the fully crystalline materials and the change in the heat capacity at the glass transition temperature for the fully amorphous nanobiocomposites), the degree of crystallinity and the mobile and rigid amorphous fractions were estimated. The addition of Cloisite®30B and aliphatic polyurethane to the P3HB matrix caused a decrease in the degree of crystallinity in reference to the unfilled P3HB. Simultaneously, an increase in the amorphous phase contents was noted. A rigid amorphous fraction was also denoted. Thermogravimetric analysis of the nanocomposites was also carried out and showed that the thermal stability of all nanocomposites was higher than that of the unfilled P3HB. An additional 1% mass of nanofiller increased the degradation temperature of the nanocomposites by about 30 °C in reference to the unfilled P3HB. Moreover, it was found that obtained hybrid nanobiocomposites containing 10 wt.% of aliphatic polyurethane (PU400) and the smallest amount of nanofiller (1 wt.% of Cloisite®30B) showed the best mechanical properties. We observed a desirable decrease in hardness of 15%, an increase in the relative strain at break of 60% and in the impact strength of 15% of the newly prepared nanobiocomposites with respect to the unfiled P3HB. The produced hybrid nanobiocomposites combined the best features induced by the plasticizing effect of polyurethane and the formation of P3HB-montmorillonite-polyurethane (P3HB-PU-MMT) adducts, which resulted in the improvement of the thermal and mechanical properties.

Application of advanced thermal analysis for characterization of crystalline and amorphous phases of carvedilol.

The thermal behaviour of crystalline and amorphous carvedilol (CAR) phases was studied by advanced thermal analysis using Quantum Design Physical Property Measurement System and Differential Scanning Calorimetry. Theoretical functions describing crystalline carvedilol heat capacity at low temperatures and the Debye-Einstein function for high temperatures were obtained. Based on the experimental heat capacity values, solid and liquid baselines were established, and the state functions (H, S, G) for solid and liquid states were calculated. A comprehensive characterization of melting and glass transition processes was obtained. CAR is easily amorphizable by cooling the liquid. The residual entropy, which quantifies the extent of frozen-in disorder in the amorphous solid, for glassy CAR was estimated as 51 J·mol-1·K-1. The Kauzmann temperature (TK) was estimated based on enthalpy and entropy. Molecular motions in the amorphous phase were also studied. The activation energy for structural relaxation (Ea = 539 kJ·mol-1) and fragility parameter (m = 91) were obtained from the non-isothermal physical ageing. The isothermal physical ageing kinetics of amorphous CAR was studied by applying Kohlrausch-Williams-Watts (KWW) model. The mean molecular relaxation time constant (τKWW = 117 min) and relaxation constant (ßKWW = 0.33) were obtained. CAR was classified as a fragile glass-former. Furthermore, τKWW constant for samples aged at 303.15 K is very low, thus, the physical ageing will occur during the short- and long-term storage of amorphous CAR, potentially changing its physicochemical properties during the ageing process. However, the results of molecular mobility studies (high molecular motions) show that the relationship between molecular motions in a glassy solid and its tendency to crystallization does not seem to follow an expected pattern, i.e., no crystallization occurred by thermal treatment of glassy, supercooled liquid and liquid phases of CAR as one would expect. Modern calorimetry and quantitative thermal analysis provided the fundamental kinetic and thermodynamic information about the crystalline and amorphous states of CAR.

Biobased poly(3-hydroxybutyrate acid) composites with addition of aliphatic polyurethane based on polypropylene glycols.

Poly(3-hydroxybutyrate) (P3HB) is the most important of the polyhydroxyalkanoates. It is biosynthesized, biodegradable, biocompatible, and shows no cytotoxicity and mutagenicity. P3HB is a natural metabolite in the human body and, therefore, it could replace the synthetic, hard-to-degrade polymers used in the production of implants. However, P3HB is a brittle material with limited thermal stability. Therefore, in order to improve its mechanical properties and processing parameters by separating its melting point and degradation temperature, P3HB-based composites can be produced using, for example, linear aliphatic polyurethanes as modifiers. The aim of the study is a modification of P3HB properties with the use of linear aliphatic polyurethanes synthesized in reaction of hexamethylene diisocyanate (HDI) and polypropylene glycols (PPG) by producing their composites. Prepared biocomposites were tested by the scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TGA). Furthermore, selected mechanical properties were evaluated. It has been confirmed that new biocomposites showed an increase in impact strength, relative strain at break, decrease of hardness and higher degradation temperature compared to the unfilled P3HB. The biocomposites also showed a decrease in the glass transition temperature and the degree of crystallinity. Biocomposites obtained with 10 wt. % polyurethane synthesized with polypropylene glycol having 1000 g ⋅ mole-1 and HDI have the best thermal and mechanical properties.

Thermally stable biopolymer composites based on poly(3-hydroxybutyrate) modified with linear aliphatic polyurethanes - preparation and properties.

PURPOSE: Poly(3-hydroxybutyrate) (P3HB) is a biopolymer, but storing products from P3HB causes the deterioration of their properties leading to their brittleness. P3HB has also low thermal stability. Its melting point almost equals its degradation temperature. To obtain biodegradable and biocompatible materials characterized by higher thermal stability and better strength parameters than the unfilled P3HB, composites with the addition of polyurethanes were produced. METHODS: The morphology, thermal, and mechanical property parameters of the biocomposites were examined using scanning electron microscopy, thermogravimetric analysis, standard differential scanning calorimetry, and typical strength machines. RESULTS: Aliphatic polyurethanes, obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycols, were used as modifiers. To check the influence of the glycol molar mass on the properties of the biocomposites, glycols with a molecular weight of 400 and 1000 g/mol were used. New biocomposites based on P3HB were produced with 5, 10, 15, and 20 wt. % content of polyurethane by direct mixing using a twin-screw extruder. The following property parameters of the prepared biocomposites were tested: degradation temperature, glass transition temperature, tensile strength, impact strength, and Brinell hardness. CONCLUSIONS: Improvement of the processing property parameters of P3HB-biocomposites with the addition of aliphatic polyurethanes was achieved by increasing the degradation temperature in relation to the degradation temperature of the unfilled P3HB by over 30 °C. The performance property parameters have also been improved by reducing the brittleness compared to the P3HB, as evidenced by the increase in impact strength and the decrease in hardness with an increase in the amount of polyurethane obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycol with a molecular weight of 400 g/mol (PU400) as modifier.

Long-Term Physical Aging Tracked by Advanced Thermal Analysis of Poly(N-Isopropylacrylamide): A Smart Polymer for Drug Delivery System.

Poly(N-isopropylacrylamide) (PNIPA), as a smart polymer, can be applied for drug delivery systems. This amorphous polymer can be exposed on a structural recovery process during the storage and transport of medicaments. For the physical aging times up to one year, the structural recovery for PNIPA was studied by advanced thermal analysis. The structural recovery process occurred during the storage of amorphous PNIPA below glass transition and could be monitored by the differential scanning calorimetry (DSC). The enthalpy relaxation (recovery) was observed as overshoot in change heat capacity at the glass transition region in the DSC during heating scan. The physical aging of PNIPA was studied isothermally at 400.15 K and also in the non-isothermal conditions. For the first time, the structural recovery process was analyzed in reference to absolute heat capacity and integral enthalpy in frame of their equilibrium solid and liquid PNIPA.

Stepwise Glucoheptoamidation of Poly(Amidoamine) Dendrimer G3 to Tune Physicochemical Properties of the Potential Drug Carrier: In Vitro Tests for Cytisine Conjugates.

Third-generation poly(amidoamine) dendrimer (PAMAM) was modified by stepwise primary amine group amidation with d-glucoheptono-1,4-lactone. The physicochemical properties of the conjugates-size, ζ potential in lysosomal pH 5 and in neutral aqueous solutions, as well as intramolecular dynamics by differential scanning calorimetry-were determined. Internalization and toxicity of the conjugates against normal human fibroblasts BJ were monitored in vitro in order to select an appropriate carrier for a drug delivery system. It was found that initial glucoheptoamidation (up to 1/3 of amine groups of neat dendrimers available) resulted in increase of conjugate size and ζ potential. Native or low substituted dendrimer conjugates accumulated efficiently in fibroblast cells at nontoxic 1 µM concentration. Further substitution of dendrimer caused consistent decrease of size and ζ potential, cell accumulation, and toxicity. All dendrimers are amorphous at 36.6 °C as determined by differential scanning calorimetry (DSC). The optimized dendrimer, half-filled with glucoheptoamide substituents, was applied as carrier bearing two covalently attached cytisine molecules: a rigid and hydrophobic alkaloid. The conjugate with 2 cytisine and 16 glucoheptoamide substituents showed fast accumulation and no toxicity up to 200 µM concentration. The half-glucoheptoamidated PAMAM dendrimer was selected as a promising anticancer drug carrier for further applications.

Hybrid nanobiocomposites based on poly(3-hydroxybutyrate) - characterization, thermal and mechanical properties.

Poly(3-hydroxybutyrate) is a biopolymer used to production of implants in the human body. On the other hand, the physical and mechanical properties of poly(3-hydroxybutyrate) are compared to the properties of isotactic polypropylene what makes poly(3-hydroxybutyrate) possible substitute for polypropylene. Unfortunately, the melting point of poly(3-hydroxybutyrate) is almost equal to its degradation temperature what gives very narrow window of its processing conditions. Therefore, numerous attempts are being made to improve the poly(3-hydroxybutyrate) properties. In the present work, hybrid nanobiocomposites based on poly(3-hydroxybutyrate) as a matrix with the use of organic nanoclay - Cloisite 30B and linear polyurethane as a second filler have been manufactured. The linear polyurethane was based on diphenylmethane 4,4'-diisocyanate and diol with imidazoquinazoline rings. The obtained nanobiocomposites were characterized by X-ray diffraction, scanning and transmission electron microscopies, thermogravimetry, differential scanning calorimetry and their selected mechanical properties were tested. The resulting hybrid nanobiocomposites have intercalated/exfoliated structure. The nanobiocomposites are characterized by a higher thermal stability and a wider range of processing temperatures compared to the unfilled matrix. The plasticizing influence of nanofillers was also observed. In addition, the mechanical properties of the discussed nanobiocomposites were examined and compared to those of the unfilled poly(3-hydroxybutyrate). The new-obtained nanobiocomposites based on poly(3-hydroxybutyrate) containing 1% Cloisite 30B and 5 wt. % of the linear of polyurethane characterized the highest improvement of processing conditions. They have the biggest difference between the temperature of degradation and the onset melting temperature, about 100 °C.