Temperature-dependent polymorphic crystalline structure and melting behavior of poly(butylene adipate) investigated by time-resolved FTIR spectroscopy

Effects of biodegradable-based microplastics in Paracentrotus lividus Lmk embryos: Morphological and gene expression analysis

Plastic pollution is a remarkable environmental issue. In fact, plastic is widespread in the lifetime and serious environmental problems are caused by the improper management of plastic end of life, being plastic litter detected in any environment. Efforts are put to implement the development of sustainable and circular materials. In this scenario, biodegradable polymers, BPs, are promising materials if correctly applied and managed at the end of life to minimize environmental problems. However, a lack of data on BPs fate and toxicity on marine organisms, limits their applicability. In this research, the impact of microplastics obtained from BPs, BMPs, were analyzed on Paracentrotus lividus. Microplastics were produced from five biodegradable polyesters at laboratory scale by milling the pristine polymers, under cryogenic conditions. Morphological analysis of P. lividus embryos exposed to polycaprolactone (PCL), polyhydroxy butyrate (PHB) and polylactic acid (PLA) showed their delay and malformations, which at molecular level are due to variation in expression levels of eighty-seven genes involved in various cellular processes, such as skeletogenesis, differentiation and development, stress, and detoxification response. Exposure to poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA) microplastics showed no detectable effects on P. lividus embryos. These findings contribute with important data on the effect of BPs on the physiology of marine invertebrates.

The effect of separation of blocks on the crystallization kinetics and phase composition of poly(butylene adipate) in multi-block thermoplastic polyurethanes

The influence of the hard segment nature on the crystallization kinetics of multi-block thermoplastic polyurethanes containing poly(butylene adipate) (PBA) as a soft segment was investigated. Using a combination of FTIR spectroscopy, time-domain ¹H nuclear magnetic resonance (TD-NMR), differential scanning calorimetry (DSC), fast-scanning calorimetry (FSC) and wide-angle X-ray diffraction (WAXS), it was shown that aliphatic, cycloaliphatic and aromatic diisocyanates affect the phase separation efficiency of soft and hard segments. The best phase separation efficiency was observed for a sample containing aliphatic diisocyanate due to the development of a hydrogen bond network. The thermal history, phase separation and the degree of ordering of the polyurethane determine the polymorphic behavior of melt-crystallized PBA. The formation of a partially-ordered mesophase of linear aliphatic polyurethane leads to an increase in the crystallization rate of PBA at room temperature and the formation of thermodynamically stable α-crystals. The presence of bulk cycloaliphatic and aromatic diol-urethane fragments prevents the phase separation of PBA, which crystallizes after slow cooling in a mixture of α- and β-crystalline forms. The new nanocalorimetry technique allows the identification of a direct correlation between the phase separation and crystallization kinetics of the melt-crystallized PBA in a wide range of cooling rates - from 2 to 30 000 K s^-1. Particularly, ultra-fast cooling suppresses the nucleation of the β-phase of PBA resulting in slow crystallization of only α-modification at room temperature. The role of the polyurethane mesophase in the crystallization of the soft segment was discussed for the first time.

Phase Transition and Melt-Recrystallization Behavior of Poly(Butylene Adipate) Investigated by Simultaneous Measurements of Wide-Angle X-Ray Diffraction (WAXD) and Differential Scanning Calorimetry (DSC)

Simultaneous measurements of wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) were carried out to investigate the phase transition and melting behaviors of poly(butylene adipate) (PBA). Thermal expansion changes along the a and b axes of the β form unit cell are different from each other during the heating process. At the beginning of the β to α_H (high-temperature α phase) phase transition, the β phase melts very fast, while the recrystallization of the α_H phase is delayed and slowed. With the further increment of the temperature, the melting rate of the β phase slows down, while the recrystallization of the α_H phase accelerates. The diffraction peak intensity ratios of the β(020):β(110) and α_H(020):α_H(110) diffraction peaks during the first heating process have similar value. However, the above value is different from the value of α(020):α(110) during the following melt-crystallization process. This difference comes from the different orientations of the crystal lattices of the α and α_H(β) crystals to the substrate plane, which indicates that the α_H phase inherits the orientation of the β phase during phase transition and the orientation of α_H form crystals is different from the α form crystals that crystallized from the melt.

Temperature dependent polymorphism of pyrazinamide: An in situ Raman and DFT study

The α and γ polymorphs of drug pyrazinamide have been detected with the help of temperature dependent Raman spectroscopic technique. Pyrazinamide is a very useful drug used for the treatment of tuberculosis (TB) and plays a significant role in destroying the dormant tubercle bacilli which are not destroyed by other common TB drugs. Temperature dependent Raman spectra suggest polymorphic phase change from α→γ form of pyrazinamide between 145 and 146°C. In situ Raman spectra of pyrazinamide between 145 and 146°C show the conversion of α→γ form by the shift in CO stretching vibration accompanied by several other changes. The phase change is characterized by the breaking of two linear NH⋯O type hydrogen bonds associated with CO stretching vibration in α dimer and formation of one linear NH⋯N type hydrogen bond along with a weak intramolecular CH⋯O type hydrogen bond in the γ dimer.

The dependence of the β-to-α phase transition behavior of poly(1,4-butylene adipate) on phase separated morphology in its blends with poly(vinylidene fluoride)

Two kinds of typical phase separated morphologies are prepared and they alter the stability of crystals.

Temperature-dependent crystalline structure and phase transition of poly(butylene adipate) end-functionalized by multiple hydrogen-bonding groups

The crystallization kinetics, crystalline structure and phase transition of UPy-functionalized poly(butylene adipate) were investigated. UPy functionalization facilitated the formation of α crystals.

Effect of Anodic Alumina Oxide Pore Diameter on the Crystallization of Poly(butylene adipate)

Poly(butylene adipate) (PBA) was infiltrated into the anodic alumina oxide (AAO) templates with the pore diameter of around 30, 70, and 100 nm and PBA nanotubes with different diameters were prepared. The crystallization and phase transition behavior of the obtained PBA nanotubes capped in the nanopores have been explored by using X-ray diffraction and differential scanning calorimetry. Only α-PBA crystals form in the bulk sample during nonisothermal crystallization. By contrast, predominant β-PBA crystals form in the AAO templates. The β-PBA crystals formed in the nanopores with pore diameter less than 70 nm prefer to adopt an orientation with their b-axis parallel to the long axis of the pore. During the melt recrystallization, it was found that the critical temperature (Tβ), below which pure β-crystals form, is 20 °C for bulk PBA. It drops down significantly with the pore diameter for the PBA in the AAO template. Moreover, the β-crystals in the porous template exhibit larger lattice parameters compared with the bulk crystals. By monitoring the change of β-crystals in the heating process, it was found that β-crystals in the AAO template with the pore diameter of 30 nm (D30) melt directly while the β-crystals transform to α-crystals in the template with the pore diameter of 100 nm (D100). The intensity of (020) Bragg peak of β-crystals decreases at a similar rate in both D30 and D100 but disappears at a relatively lower temperature in D30. On the other hand, the β(110) peak intensity of β-PBA crystals formed in the D100 template decreases first at slower rate before α crystals appear, and then at a faster rate once the β to α phase transition takes place.

The phase transition behavior of poly(butylene adipate) in the nanoporous anodic alumina oxide

PBA nanotubes with different diameters have been prepared.

Intertwining lamellar assembly in porous spherulites composed of two ring-banded poly(ethylene adipate) and poly(butylene adipate)

Poly(1,4-butylene adipate) (PBA) and poly(ethylene adipate) (PEA), each with the ability to form ring-banded morphologies at same Tc, were simultaneously crystallized from mixtures of various compositions. Investigations on morphology, phase and thermal behavior were conducted in order to reveal lamellar packing and spherulitic structures in this binary system. As PBA is faster-crystallizing and dominates the crystallization process, it is relatively easy to maintain its ordered ring-banded pattern in a PBA/PEA blend when there is a moderate amount of PBA in the composition (40 wt% or greater). On the other hand, PEA is much slower crystallizing and it has to be in extreme majority (PEA > 95 wt%) in the PBA/PEA mixtures in order to crystallize into ring-banded spherulites of PEA pattern. When PBA composition is between 10 and 40 wt% in the PBA/PEA blend, simultaneous crystallization of PBA and PEA leads to an interpenetrating morphology with an interwoven bird-nest pattern. Porous structures with crevices, owing to the interpenetrating PBA and PEA lamellae, resulted in simultaneous crystallization of these two biodegradable polyesters.

Novel polymorphism behavior of poly(butylene adipate) in its nanocomposites with carbon nanofibers

Carbon nanofibers prominently enhance the formation of α-form crystal poly(butylene adipate) at low temperature and lead to a novel plateau phenomenon of α-form crystal content in their composites through specific CH–π interactions.