Recent applications of the Successive Self-nucleation and Annealing thermal fractionation technique

Successive Self-nucleation and Annealing (SSA) is a thermal fractionation technique that is performed by Differential Scanning Calorimetry (DSC). The combination of non-isothermal and isothermal steps applied during SSA achieves efficient molecular segregation during polymer crystallization. Such molecular segregation magnifies the effect of defects in polymer chain crystallization, thereby providing information on chain structure. The technique was created and implemented by Müller and co-workers in 1997, becoming a powerful resource for studying ethylene/α-olefin copolymers. The different variables to design the SSA protocol: fractionation window, fractionation time, scanning rate, sample mass, and the first self-nucleation temperature to be applied (Ts, ideal), have been previously reviewed, together with the different applications of SSA. SSA versatility, simplicity (when properly applied), and short times to produce results have allowed its use to study novel and more complex polymeric systems. This review article explores the most recent applications of SSA of the past decade. First, the principles of the technique are briefly explained, covering all the relevant variables. Next, we have selected different cases that show how SSA is employed in various novel fields, such as studying intermolecular interactions and topological effects in homopolymers; supernucleation and antinucleation effects in nanocomposites, including the pre-freezing phenomenon; crystallization modes in random copolymers; solid-solid transitions; miscibility, co-crystallization and composition in blends; evaluation of polymer synthesis variables; and the novel information that could be gained by using fast scanning chip-based calorimetry. Finally, we offer a perspective on SSA, a technique that has become a powerful method for studying the distribution of defects affecting crystallization in semi-crystalline polymers.This work has received funding from the Basque Government through grant IT1503-22 and from MICINN (PID2020-113045GB-C21). We would also like to acknowledge the financial support from the BIODEST and the REPOL projects; these projects have received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreements No. 778092 and No. 860221. It has also been supported by the National Natural Science Foundation of China (51820105005, 52050410327)

Using Successive Self-Nucleation and Annealing to Detect the Solid−Solid Transitions in Poly(hexamethylene carbonate) and Poly(octamethylene carbonate)

Unformatted post-print version of the accepted articleSolid-solid transitions in poly (hexamethylene carbonate) (PC6) and poly (octamethylene carbonate) (PC8), denoted δ to α transition, have been investigated, using self-nucleation and Successive Self-nucleation and Annealing (SSA) technique. The SSA protocol was performed in-situ for thermal (differential scanning calorimetry (DSC)), structural (Wide-angle X-ray Scattering (WAXS)), and conformational (Fourier-transformed Infrared Spectroscopy (FT-IR)) characterization. The final heating after SSA fractionation displayed an enhanced (compared to a standard second DSC heating scan) endothermic and unfractionated peak signal at low temperatures corresponding to the δ to α transition. The improved (i.e., higher enthalpy and temperature than in other crystallization conditions) δ to α transition signal is produced by annealing the thickest lamellae made up by α and β phase crystals after SSA treatment. As thicker lamellae are annealed, more significant changes are produced in the δ to α transition, demonstrating the transition dependence on crystal stability, thus, on the crystallization conditions. The ability of SSA to significantly enhance the observed solid-solid transitions makes it an ideal tool to detect and study this type of transitions. In-situ WAXS reveals that the δ to α transition corresponds to a change in the unit cell dimensions, evidenced by an increase in the d-spacing. This implies a more efficient chain packing in the crystal, for both samples, in the δ phase (lower d-spacing at low temperatures) than in the α phase (higher d-spacing at high temperatures). The chain packing differences are explained through in-situ FT-IR measurements that show the transition from ordered (δ phase) to disordered (α phase) methylene chain conformations.We would like to acknowledge financial support provided by the National Key R&D Program of China (2017YFE0117800) and the National Natural Science Foundation of China (51820105005, 21922308, and 52050410327). We also acknowledge financial support from the BIODEST project; this project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 778092. This work has also received funding from MINECO through project MAT2017-83014-C2-1-P and from the Basque Government through grant IT1309-19. R.A.P.-C is supported by the China Postdoctoral Science Foundation (2020M670462). G.L. is grateful to the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Y201908). We also thank the BSRF (beamline 1W2A) for providing beamtime

Solid–Solid Crystal Transitions (δ to α) in Poly(hexamethylene carbonate) and Poly(octamethylene carbonate)

Unformatted post-print version of the accepted articlePoly (hexamethylene carbonate) (PC6) and poly (octamethylene carbonate) (PC8) were studied under different crystallization conditions. Using differential scanning calorimetry (DSC), a new solid-solid transition, denoted α to δ transition, was detected at low temperatures (<RT) in both PC6 and PC8 samples. The α to δ transition was represented by exothermic (i.e., α to δ) (−6 °C (PC6) and −20 °C (PC8)) and endothermic peaks (i.e., δ to α) (15 °C (PC6) and 28 °C (PC8)), during cooling and heating DSC scans, respectively. Isothermal tests revealed that this solid-solid transition depends on the specific thermal history, since it is not observed at isothermal temperatures higher than room temperature. Still, it is detected in the subsequent cooling and heating scans. Wide-angle X-ray scattering (WAXS) and Fourier-transform infrared spectroscopy (FT-IR) experiments were performed at identical conditions to those by DSC. WAXS experiments showed lower d-spacings in the δ phase than in the α one, corresponding to a unit cell shrinkage, explained by a more efficient packing of the methylene groups in the δ phase. The δ phase is also characterized, according to FT-IR experiments, by more ordered conformation of the methylene groups (i.e., reflected in the appearance of a new absorption band) compared to the less ordered conformation in the α phase.This work is supported by the National Key R&D Program of China (2017YFE0117800) and the National Natural Science Foundation of China (51820105005, 21922308, and 52050410327). We would like to thank the financial support provided by the BIODEST project; this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 778092. This work has also received funding from MINECO through project MAT2017-83014-C2-1-P and from Basque Government through grant IT1309-19. R.A.P.-C is supported by the China Postdoctoral Science Foundation (2020M670462). G.L. is grateful to the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Y201908). We also thanks to the BSRF (beamline 1W2A)

Unexpected structural properties in the saturation region of the odd-even effects in aliphatic polyethers: Influence of crystallization conditions

Unformatted post-print version of the accepted articleA series of aliphatic polyethers with different chain lengths (nCH2= 6 to 12, and 16) is studied employing differential scanning calorimetry and X-rays scattering. The calorimetric and structural behavior of samples crystallized from the melt is divided into the odd-even and saturation regions. In the odd-even region (nCH2 = 6 to 10), the odd samples (nCH2 = 7, and 9) show enhanced calorimetric properties (e.g., higher transition temperatures) and faster crystallization kinetics than the even ones (nCH2 = 6, 8 and 10). The odd samples crystallize in orthorhombic unit cells and the even ones in monoclinic unit cells. In the saturation region (nCH2 = 11 to 16), the calorimetric properties increase as nCH2 increases without alternation. However, unexpectedly, the nCH2 = 12 displayed a mixed structure (monoclinic + orthorhombic) instead of an orthorhombic one. Thus, a structural saturation effect (i.e., an orthorhombic unit cell) is not reached. This particular structural feature was investigated under varied thermal histories, induced by different cooling rates. The samples as synthesized (i.e., crystallized during precipitation from solution) exhibited a structural saturation effect since both nCH2 = 10 and 12 display an orthorhombic unit cell. But, the nCH2 = 10 exhibits a monoclinic unit cell, and the nCH2 = 12 a mixed structure when the samples crystallize from the melt at different rates. Only the nCH2 = 16 crystallizes in an orthorhombic unit cell, independently of the thermal history. Thus, the complex odd-even effects in these aliphatic polyethers are a function of the cooling rate from the melt and sample preparation procedures (solution or melt crystallization).We would like to thank the financial support provided by the BIODEST project; this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 778092. This work was also supported by Grant PID2020-113045GB-C21 funded by MCIN/AEI/10.13039/501100011033. This work has also received funding from the Basque Government through grant IT1309-19. R.A.P.-C is supported by the China Postdoctoral Science Foundation (2020M670462), and National Natural Science Foundation of China (NSFC) (52050410327). The support of the ALBA (2020024169) and SSRF synchrotron facility is gratefully acknowledged

Accelerating the crystallization kinetics of linear polylactides by adding cyclic poly (L-lactide): Nucleation, plasticization and topological effects

Unformatted post-print version of the accepted articlePolylactide is one of the most versatile biopolymers, but its slow crystallization limits its temperature usage range. Hence finding ways to enhance it is crucial to widen its applications. Linear and cyclic poly (L-lactide) (l-PLLA and c-PLLA) of similarly low molecular weights (MW) were synthesized by ring-opening polymerization of L-lactide, and ring-expansion methodology, respectively. Two types of blends were prepared by solution mixing: (a) l-PLLA/c-PLLA, at extreme compositions (rich in linear or in cyclic chains), and (b) blends of each of these low MW materials with a commercial high MW linear PLA. The crystallization of the different blends was evaluated by polarized light optical microscopy and differential scanning calorimetry. It was found, for the first time, that in the l-PLLA rich blends, small amounts of c-PLLA (i.e., 5 and 10 wt%) increase the nucleation density, nucleation rate (1/τ0), spherulitic growth rate (G), and overall crystallization rate (1/τ50%), when compared to neat l-PLLA, due to a synergistic effect (i.e., nucleation plus plasticization). In contrast, the opposite effect was found in the c-PLLA rich blends. The addition of small amounts of l-PLLA to a matrix of c-PLLA chains causes a decrease in the nucleation density, 1/τ0, G, and 1/τ50% values, due to threading effects between cyclic and linear chains. Small amounts of l-PLLA and c-PLLA enhance the crystallization ability of a commercial high MW linear PLA without affecting its melting temperature. The l-PLLA only acts as a plasticizer for the PLA matrix, whereas c-PLLA has a synergistic effect in accelerating the crystallization of PLA that goes beyond simple plasticization. The addition of small amounts of c-PLLA affects not only PLA crystal growth but also its nucleation due to the unique cyclic chains topology.We would like to acknowledge the financial support from the BIODEST project; this project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 778092. This work has also received funding from the Basque Government through grant IT1309-19. R.A.P.-C is supported by PIFI of the Chinese Academy of Science for international postdoctoral researchers (2019PE0004), the China Postdoctoral Science Foundation (2020M670462), and National Natural Science Foundation of China (NSFC) (52050410327) under the program Research Fund for International Young Scientists. O.C. is Senior Research Associate for the F.R.S.-FNRS of Belgium

Crystallization and morphology of multiphasic polymeric systems: random copolymers, nanocomposites and polymers with complex chain topologies.

323 p.En el presente trabajo se caracterizaron térmica, estructural y morfológicamente diferentes sistemas multifásicos, entre los que se incluyen: (a) copoliésteres al azar con diferentes unidades repetitivas y comportamiento isodimórfico; (b) copolímeros con distribución de comonómero tipo gradiente y semi-azar con diferentes arquitecturas moleculares: tipo lineal, estrella y peines con longitud de brazos y grados de polimerización diferentes por brazo; (c) sistemas basados en lignina, entre los que se encuentran copolímeros de poli (¿-caprolactona) (PCL) con injertos de lignina y mezclas de poli (ácido láctico) con lignina industrial y talco; (d) sistemas basados en nanotubos de carbonos, en los que se mezcló PCL con (i) nanotubos puros; (ii) nanotubos con injertos de PCL; (iii) nanotubos dispersos en masterbatch basado en policarbonato. Adicionalmente dicho masterbatch también fue mezclado con unamatriz de poli (butilén succinato). (e) PCL cíclica (C-PCL) y lineal (L-PCL) y sus mezclas en diferentes proporciones y con dos diferentes pesos moleculares promedio en número.El estudio de los sistemas arriba expuestos permitió hallar y comprender comportamientos variados tales como: la cristalización isodimórfica y la influencia de la distribución de comonómeros sobre ella; la influencia de la topología, longitud de cadena y número de brazos en copolímeros semi-azar, efectos supernucleantes, nucleantes y anti-nucleantes en sistemas basados en lignina, al igual que en sistemas basados en nanotubos de carbono, y la influencia de la topología de cadena (lineal vs cíclica) en mezclas (C/L) de PCL

Experimental and Data Fitting Guidelines for the Determination of Polymer Crystallization Kinetics

The crystallization kinetics of semicrystalline polymers is often studied with isothermal experiments and analyzed by fitting the data with analytical expressions of the Avrami and Lauritzen and Hoffman (LH) theories. To correctly carry out the analysis, precautions both in experiments and data fitting should be taken. Here, we systematically discussed the factors that influence the validity of the crystallization kinetics study. The basic concepts and fundamentals of the Avrami and LH theories were introduced at first. Then, experimental protocols were discussed in detail. To clarify the impact of various experimental parameters selected common polymers, i.e., polypropylene and polylactide, were studied using various experimental techniques (i.e., differential scanning calorimetry and polarized light optical microscopy). Common mistakes were simulated under conditions when non-ideal experimental parameters were applied. Furthermore, from a practical point of view, we show how to fit the experimental data to the Avrami and the LH theories, using an Origin ® App developed by us.This work was financially supported by the the National Natural Science Foundation of China (Nos. 21922308 and 51820105005) and the National Key R&D Program of China (No. 2017YFE0117800). We would also like to acknowledge the financial support from the BIODEST project; this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 778092. The funding of MICINN (Spain) through grant PID2020-113045GB-C21 is gratefully acknowledged. G. L. is grateful to the Youth Innovation Promotion Association of the Chinese Academy of Sciences (No. Y201908

Effect of the Crystallization Conditions on the Exclusion/Inclusion Balance in Biodegradable Poly(butylene succinate- ran-butylene adipate) Copolymers

none5Biomedical applications of polymers require precise control of the solid-state structure, which is of particular interest for biodegradable copolymers. In this work, we evaluated the influence of crystallization conditions on the comonomer exclusion/inclusion balance of biodegradable poly(butylene succinate-ran-butylene adipate) (PBSA) isodimorphic random copolymers. Regardless of the crystallization conditions, the copolymers retain their isodimorphic character, displaying a pseudo-eutectic behavior with crystallization in the entire composition range. This illustrates the thermodynamic nature of the isodimorphic behavior for PBSA random copolymers. However, depending on the composition, the crystallization conditions affect the exclusion/inclusion balance of the comonomers. Fast cooling favors butylene adipate (BA) inclusion inside the poly(butylene succinate) (PBS) crystals, whereas isothermal crystallization strongly limits it. PBA-rich compositions behave differently. Both fast and slow crystallization formed the β-phase, whereas BS unit inclusion is favored independently of the cooling conditions. During successive self-nucleation and annealing, the BA inclusion is intermediate between non-isothermal and isothermal conditions, while the crystalline structure of the PBA phase changes from the β-phase to the more stable α-phase. We propose a simple crystallographic model to explain the changes in the unit cell dimension of the copolymers.nonePerez-Camargo R.A.; Liu G.; Cavallo D.; Wang D.; Muller A.J.Perez-Camargo, R. A.; Liu, G.; Cavallo, D.; Wang, D.; Muller, A. J

Even-odd Effect in Aliphatic Polycarbonates with Different Chain Lengths: from Poly (hexamethylene carbonate) to Poly (dodecamethylene carbonate)

Unformatted post-print version of the accepted articleWe have characterized a series of aliphatic polycarbonates synthesized by organocatalysis containing a variable number of methylene groups (nCH2) in their repeat units ranging from nCH2 = 6 to 12. The melting and crystallization behavior and crystalline structures were studied by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), and wide-angle X-ray scattering (WAXS). We found a clear even-odd effect in terms of thermal properties and crystalline structure, for nCH2 = 6 to 9, and a saturation of the even-odd effect, for nCH2 = 10 to 12. These results were independent of the crystallization conditions employed: non-isothermal, isothermal and successive self-nucleation and annealing (SSA). The even-odd region showed that the even samples had higher melting temperatures than the odd ones, and a monoclinic unit cell. On the other hand, the odd samples showed an orthorhombic unit cell. Both even and odd samples exhibited a trans-conformation, with a dilution of the impact of carbonyl group as evidenced by the weakening of the crystalline memory effect as nCH2 increases, independently of the even or odd nature of the samples. In the saturation region, the methylene instead of the carbonyl groups dominated the behavior, resulting in thermal properties that changed almost linearly with nCH2. The unit cells were all orthorhombic and the strength of memory effect was similar, as nCH2 increased. Accordingly, the samples showed a shift of the FTIR bands towards a PE-like dominated conformation.This work is supported by the National Key R&D Program of China (2017YFE0117800) and the National Natural Science Foundation of China (51820105005, 21922308, and 52050410327). We would like to thank the financial support provided by the BIODEST project; this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 778092. This work has also received funding from MINECO through project MAT2017-83014-C2-1-P and from the Basque Government through grant IT1309-19. R.A.P.-C. is supported by PIFI of the Chinese Academy of Science for international postdoctoral researchers (2019PE0004), and the China Postdoctoral Science Foundation (2020M670462). G.L. is grateful to the Youth Innovation Promotion Association of the Chinese Academy of Sciences (Y201908). L.M. thanks Spanish Ministry of Education, Culture, and Sport for the predoctoral FPU fellowship received to carry out this work