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Comprehensive Summary: A disulfide‐based poly(ether‐b‐amide) copolymer with rapid self‐healing capability under moderate conditions was synthesized from 4,4'‐dithiodibutyric acid (DTDBA), isophorondiamine (IPDA) and poly(tetramethylene oxide) (PTMO) based on a two‐step method. The incorporation of IPDA with asymmetric structure and substantial steric hindrance not only effectively decreased the number of regular H‐bonds, but also inhibited the crystallization of polyamide segments, imparting the synthesized poly(ether‐b‐amide) copolymer with an amorphous structural feature. Based on the coordination of segmental diffusion and recombination of disulfide bonds and hydrogen bonds, the scratches and damaged mechanical properties of PEBADS‐I611 could be completely self‐healed after healing at 40 °C for only 11 min and 3 h, respectively. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of surface properties of nanoparticles (NPs) on the crystallization behavior of nanocomposite, three kinds of silica (SiO2) NPs are dispersed in isotactic polypropylene (iPP) matrix by solution blending method. Specifically, the poor compatibility between inorganic bare SiO2 NPs and organic PP matrix triggers the formation of aggregates and induces the fractionated crystallization with two crystallization peaks at higher particle loading (Φ), i.e., main crystallization peak (MCP) and low temperature crystallization peak (LCP, always located at 124.0 °C). Once short PP chains (0.9 × 104 g mol−1) are grafted onto the surface of SiO2 NPs, the nanocomposites with all Φ only exhibit a single MCP which is attributed to the strong interfacial interaction. With the increase of grafting chain length (9 × 104 g mol−1), the more stretched conformation of grafting chains can provide numerous heterogeneous nucleation sites and significantly accelerate the crystallization rate of PP chains near the surface of SiO2 NPs, which lead to the formation of an extra high temperature crystallization peak (HCP, almost kept constant at 133.0 °C). The occurrence of various crystallization peaks implies that the surface properties of nanoparticles play a vital role in the nucleation ability of nanoparticles. [ABSTRACT FROM AUTHOR]

The high crystallinity and fast crystallization rate of polypropylene (PP) often result in severe warpage of final parts prepared by means of material extrusion additive manufacturing (MEAM). In this work, the effect of bed temperature (Tb) and nozzle temperature (Tn) on the dimensional accuracy and mechanical property of MEAM‐printed PP copolymer parts was investigated. It is found that raising Tb and Tn could significantly reduce the warpage of PP parts by regulating the crystallization behavior of PP. Specially, the amount of γ‐crystal grows obviously while the total crystallinity remains unchanged, as Tb or Tn increases. Moreover, the more the content of γ‐crystal, the lower the warpage height of PP samples is. Hence, a close correlation between the content of γ‐crystal and part deformation of MEAM‐printed PP parts is successfully established. This is mainly related to the large rigidity of γ‐crystal, which significantly reduces the volume shrinkage of PP during MEAM process. Besides, the raise of Tb or Tn also enhances the tensile strength, modulus and the elongation at break of PP parts. This wok provides an effective and convenient method for the manufacture of PP parts with good dimensional accuracy and excellent mechanical properties by means of MEAM techniques. [ABSTRACT FROM AUTHOR]

The interplay between crosslinks and crystals is critical for the mechanical properties and applications of Eucommia ulmoides gum (EUG). In this work, EUG samples with different crosslink densities are prepared by sulfur vulcanization. The effect of crosslink density on the crystallization, melting, and mechanical properties are systematically investigated. As expected, crosslinks suppress the crystallization of EUG, resulting in a decrease in melting/crystallization temperature, crystallinity, modulus, and yield stress. Interestingly, vulcanized EUG can gradually crystallize during annealing at room temperature, showing a nonequilibrated state and slow crystallization kinetics. Correspondingly, the modulus increases with the annealing time. Cyclic deformation tests show that EUG vulcanizates have a lower hysteresis loss in the first cycle but a much higher hysteresis loss for subsequent cycles, showing the potential to have low-frequency damping properties. In situ wide-angle X-ray diffraction demonstrates that the hysteresis loss of EUG depends significantly on strain-induced crystallization/melting. [ABSTRACT FROM AUTHOR]

We studied the crystallization of nearly "homogeneous" polyethylene glycol (PEG) networks prepared by end-crosslinking of tetra-armed PEG. The influence of stretching ratio and strand length on the melting and crystallization temperature was investigated. The relation of melting temperature and elongation ratio verifies the thermodynamic theories of strain-induced polymer crystallization. [ABSTRACT FROM AUTHOR]

Hydrothermal aging behavior of polyamide 6 (PA6) and its composites (PA6/calcium carbonate [CaCO3] and PA6/short glass fiber [SGF]) was systematically investigated using infrared spectroscopy, dynamic mechanical analysis, differential scanning calorimetry, and wide‐angle X‐ray diffraction as well as mechanical measurements. It was found that the water absorption mechanism is strongly affected by the presence of fillers. SGF‐reinforced PA6 composites absorb less water than PA6 and PA6/CaCO3 composites under the same hydrothermal condition. PA6 with 10 wt% SGF exhibits great resistance to hydrothermal aging, which is attributed to the higher crystallinity and larger α‐form fraction. [ABSTRACT FROM AUTHOR]

Shear flow strongly affects the polymorphism and crystallization kinetics of semi‐crystalline polymers. In the present work, the crystallization behavior of a β‐nucleated propylene‐ethylene (P‐E) random copolymer was studied both under quiescent and shear flow by using in‐situ wide‐angle X‐ray diffraction. It was observed that shear flow could shorten the induction time, fasten the crystallization rate and increase the degree of crystallinity. The populations of different crystal modifications varied significantly upon shearing. Especially the β crystals fraction decreased with shear strain. When the shear strain was higher than 100 with a fixed shear rate of 5 s−1, the β crystals almost disappeared. Meanwhile, both the fractions and the crystallization rates of α and γ crystals were enhanced by shear flow. The complicated polymorphic behavior can be interpreted by the nucleation kinetics. [ABSTRACT FROM AUTHOR]

Investigation of microstructure and properties is critical for the development and application of polymer materials. Polypropylene random copolymer ( PPR) and β-nucleated PPR are widely used in water pipe production. The effect of melt shear flow on the crystalline structure and mechanical properties of PPR containing β-nucleating agent needs in-depth understanding. In this paper, we demonstrated the preparation of PPR and PPR containing 0.1 wt% calcium pimelate (Ca-Pim) samples by conventional injection molding ( CIM) and oscillation shear injection molding ( OSIM). The multilayer structures and morphologies of the samples were characterized by SEM, two-dimensional X-ray scattering and DSC. The mechanical properties and the microstructures of samples prepared by these two injection molding methods were compared. Compared with samples prepared by CIM, the stronger shear provided by OSIM induced the formation of a thicker layer of a shish-kebab structure and a higher content of γ crystals, and dramatically suppressed the β-nucleating effect of Ca-Pim. The OSIM samples have more shish-kebab structures and higher crystallinities than CIM samples and therefore the former exhibit better rigidity than the latter. The β crystals in the core layer and the thicker layer of shish-kebab structure endow OSIM-PPR/0.1 wt% Ca-Pim with excellent impact toughness. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

ABSTRACT The confinement effects introduced by nanoparticles have been reported to influence the phase behaviors thus the properties of polymer nanocomposites. In this study, molecular dynamics and crystallization behaviors of polyethylene (PE) composited with three types of silica (SiO2) nanoparticles, namely unmodified SiO2, hydrophobically modified SiO2, SiO2-APTES (3-aminopropyltriethoxysilane) and SiO2-PTES ( n-propyltriethoxysilane), were systematically investigated via a combination of DSC, XRD and 1H solid-state NMR measurements. The suppressions in crystallization and chain mobilities of PE rank in the order of unmodified SiO2 < SiO2-APTES < SiO2-PTES due to the increasing interfacial interactions between PE and SiO2 nanoparticles. Additionally, independent of polymer-nanoparticle interactions, a silica network forms for all three kinds of nanocomposites when SiO2 content reaches 83 wt %. The mobilities of polymer chains are severely restricted by such a percolated network structure, leading to a turning point in the crystallization ability of nanocomposites and a new crystallization peak at 45 °C lower than that of pure PE. The synergetic effects of interfacial interactions and filler network on polymer crystallization have been thoroughly studied in this work, which will provide guidance on modifying and designing nanocomposites with controlled properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 498-505 [ABSTRACT FROM AUTHOR]

ABSTRACT Compared with the most stable crystalline form of isotactic polypropylene (α-iPP), β-iPP shows superior impact strength and high temperature performance, though the mechanism of how the frustrated structure of β-iPP is formed still remains unclear. In present work, the single crystal structure of a traditional β-iPP nucleating agent, N, N′-dicyclohexylterephthalamide (DCHT), was obtained for the first time and correlated with the epitaxial crystallization of β-iPP on the surface of DCHT crystal. The combination of synchrotron radiation X-ray microdiffraction and molecular chain packing model confirmed that a two dimensional match of chain-axis and inter-chain direction coexists between β-iPP (110) plane and DCHT (001) plane. It was further found that an epitaxial model is helpful to understand the formation of the frustrated structure of 31 helices packing in β-iPP. The molecular mechanics computation showed that as the (001) plane of DCHT is fixed, the packing mode of β-iPP (110) plane on the substrate surface is more stable than that of α-iPP (010) plane. This work clarifies the epitaxial crystallization mechanism of β-iPP on DCHT by employing both experimental and computational evidences. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 418-424 [ABSTRACT FROM AUTHOR]

ABSTRACT Poly(butylene succinate- ran-butylene azelate) random copolyesters were thermally fractionated by successive self-nucleation and annealing (SSA). The samples before and after SSA were analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (WAXS and SAXS). WAXS results indicate that a small degree of comonomer inclusion is present in the crystalline phases that are formed in the copolymers depending on composition: a PBS-like unit cell or/and a PBAz-like unit cell, thus confirming the isodimorphic behavior of the samples. SSA on the other hand demonstrated that the degree of comonomer exclusion during crystallization is far larger than comonomer inclusion, as judged by the increase in fractionation degree with compositions leading to the pseudo-eutectic point. Furthermore, WAXS, SAXS, and SSA results show that the isodimorphic behavior is not highly dependent on kinetic factors, as the degree of comonomer inclusion or exclusion in the samples was not significantly altered by SSA thermal fractionation, a thermal treatment that promotes annealing and molecular segregation of defects to the amorphous regions of the material. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2346-2358 [ABSTRACT FROM AUTHOR]

The effect of the final melting temperature (Tf) on the crystallization of poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA) was studied via a combination of differential scanning calorimetry, wide-angle X-ray scattering, polarized optical microscopy, and Fourier transform infrared (FTIR) spectroscopy. We observed that a residual stereocomplex (SC) crystal induced the formation of SC crystals during cooling from a Tf (230°C) just above the melting peak of the SC crystals. On cooling from a Tf (240°C) just above the endset temperature of SC crystal melting [Tm(S)(E)], the possible order structure and the strong interchain interaction promoted the preferential crystallization of SC crystals; this enhanced the formation of a crystals. During cooling from a Tf (≥250°C) far above Tm(S)(E), the crystallization peaks of a and SC crystals converged. The FTIR results indicated that the residual SC crystals, possible ordered structure, and interchain interactions in the melt might have been the key factors for the different crystallization of PLLA/PDLA. [ABSTRACT FROM AUTHOR]

ABSTRACT Propylene-based propylene-ethylene random copolymer (PPR) has been widely used in the production of hot-water pipes. To further improve its toughness and thermal resistance, β-nucleating agents (β-NAs) are frequently incorporated. In this study, PPR containing 5.6 mol % ethylene units was modified by two kinds of β-NAs, that is, calcium pimelate and N,N′-dicyclohexylterephthalamide. The notched Izod impact strength of PPR increased with the addition of the β-NAs. Drastically different toughening effects were found between the two β-NAs. The structure of PPR with and without a β-NA was investigated by calorimetry, X-ray diffraction, and thermomechanical analysis. The results indicated that the relative fraction of β crystals ( kβ) in the injection-molded specimens was determined by the type and content of β-NA. The relationship between kβ and the impact toughness was summarized. A critical value for kβ (0.68) was identified for the brittle-ductile transition of PPR. PPR with β-NA having a kβ greater than 0.68 displayed a higher impact strength than the other mixtures. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42930. [ABSTRACT FROM AUTHOR]

ABSTRACT The impact of nanoconfinement introduced by nanoparticles on polymer crystallization has attracted extensive attention because it plays an important role in the ultimate properties of polymer nanocomposites. In this study, interfacial and spatial confinement effects of silica (SiO2) nanoparticles on the crystallization behaviors of poly(ethylene oxide) (PEO)/SiO2 composites were systematically investigated by changing the size and concentration of SiO2 in PEO matrix. The composites with high silica loadings exhibit two crystallization peaks of PEO as determined by differential scanning calorimetry. The first peak at 7-43 °C is related to the bulk PEO, while the second peak at −20 to −30 °C is attributed to the restricted PEO segments. Three-layer (amorphous, interfacial, and bulk) model is proposed to interpret the confined crystallization of PEO/SiO2 composites, which is supported by the results of thermogravimetric analysis and solid-state 1H nuclear magnetic resonance. In amorphous layer, most PEO segments are directly adsorbed on SiO2 surface via hydrogen bonding. The interfacial PEO layer, which is nonuniform, is composed of crystallizable loops and tails extending from amorphous layer. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 414-423 [ABSTRACT FROM AUTHOR]

ABSTRACT The influence of short-chain branching on the formation of single crystals at constant supercooling is systematically studied in a series of metallocene catalyzed high-molecular-weight polyethylene samples. A strong effect of short-chain branching on the morphology and structure of single crystals is reported. An increase of the axial ratio with short-chain branching content, together with a characteristic curvature of the (110) crystal faces are observed. To the best of our knowledge, this is the first time that this observation is reported in high-molecular-weight polyethylene. The curvature can be explained by a continuous increase in the step initiation-step propagation rates ratio with short-chain branching, that is, nucleation events are favored against stem propagation by the presence of chain defects. Micro-diffraction and WAXS results clearly indicate that all samples crystallize in the orthorhombic form. An increase of the unit cell parameter a0 is detected, an effect that is more pronounced than in the case of single crystals with ethyl and propyl branches. The changes observed are compatible with an expanded lattice due to the presence of branches at the surface folding. A decrease in crystal thickness with branching content is observed as determined from shadow measurements by TEM. The results are in agreement with additional SAXS results performed in single crystal mats and with indirect calorimetry measurements. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1751-1762 [ABSTRACT FROM AUTHOR]

A low molecular weight aliphatic amide, N, N′-ethylenebis (12-hydroxystearamide) (EBH), was selected to tailor the crystallization behavior of poly ( l-lactide) (PLLA). The effect of EBH on the crystallization kinetics, fine crystalline structure, and molecular mobility of PLLA has been systematically investigated. It has been found that the crystallizability of PLLA, including crystallization rate and crystallinity, can be promoted significantly by the addition of only 1 wt% EBH. Both the nucleation density and linear growth rate of spherulites have been improved, which together contributed to the decrease of overall crystallization time. The long period and lamellar thickness of PLLA crystals increased gradually with the isothermal crystallization temperature, whereas they were less influenced by the incorporation of EBH. Dynamic mechanical analysis proved that the mobility of PLLA chains was also increased in the presence of EBH. The accelerating effect of EBH on both the nucleation and molecular mobility of PLLA was supposed to be the hydrogen-bonding interaction between the hydroxyl groups in EBH and carboxyl groups in PLLA. [ABSTRACT FROM AUTHOR]

A low molecular weight hydrazide compound, tetramethylenedicarboxylic di (2-hydroxybenzohydrazide) (TMBH), greatly improves the crystallization rate and crystallinity of poly( l-lactide) (PLLA). The nucleating efficiency of TMBH on the crystallization of PLLA exhibits obvious concentration dependence, which increases first and then decreases slightly with the increase of TMBH loading, reaching a maximum at 0.3 wt%. Time-resolved Fourier transform infrared spectroscopy spectra indicate that the formation of skeletal conformational ordering structure of PLLA has been accelerated in the presence of TMBH, which can act as efficient precursors speeding up both the nucleation of PLLA on TMBH surface and the formation of intrachain 103 helix structure. The possible hydrogen bonding interaction between the OH or NH groups in TMBH and the CO groups in PLLA backbones is supposed to be an important factor, which promotes the migration of PLLA chains to TMBH crystallites and the emergence of interchain interactions as well as the conformational ordering. [ABSTRACT FROM AUTHOR]

ABSTRACT In the present work, the fracture behavior of transcrystallization (TC) of poly( l-lactic acid) (PLLA) in thin film and the dependence of mechanical properties on the morphology of TC have been studied. The nucleation density of TC was merely determined by the annealing temperatures of the fibers which used for inducing nucleation, and the crystallization temperature and time of the samples were completely identical. By using in situ polarized optical microscopy, the fracture process of TCs was characterized. For the TC with high nucleating density (TC-H), lots of cracks were generated from the TC bulk during fracture. But only few cracks were observed on the TC with low nucleation density (TC-L), and the final fracture of TC-L always occurred in the junctions of crystal segments. Compared to the samples which do not contain TC, the fracture strength was enhanced by 8.1% because of the presence of TC-H. On the contrary, the presence of TC-L can reduce the fracture strength of the samples. The fracture surfaces of TC were characterized by scanning electron microscope. It was observed that the fracture surface of TC-H exhibited obvious fibrillation and cavitation, but the fracture surface of TC-L was smooth and featureless. The possible fracture mechanism for two TCs was discussed in view of their intrinsic crystal organizations. © 2014 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41273. [ABSTRACT FROM AUTHOR]

We report on the confined crystallization and polymorphism behavior of a series of comb-like polymers (CS(n)Cs), which were prepared viaan N-alkylation reaction between chitosan and n-alkyl bromides (n= 14–20). Analysis by temperature-dependent synchrotron X-ray scattering, Fourier transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance spectroscopy (NMR) and differential scanning calorimetry (DSC) revealed that the phase transition and crystalline structure were sensitively controlled by the length scale and the confinement state of alkyl groups, which could induce different packing structures and conformational variation behavior. Remarkably, phase transition from orthorhombic-hexagonal to monoclinic structure was observed for these side-chain polymers, demonstrating that the length scales of alkyl groups and the microstructure of polymeric backbones play an important role in the evolution of packing mode of nano-crystallites. [ABSTRACT FROM AUTHOR]

A transparent polyamide, poly(4,4′-aminocyclohexyl methylene dodecanedicarboxylamide) (PAPACM12), was studied and characterized by in situ wide-angle X-ray diffraction (WAXD) to establish the relationship between its crystallization behavior, crystalline form transition under external fields, and macroscopic properties. During the heating process, cold crystallization occurred and increased, and there was no form transition below the melting point. During the isothermal process, PAPACM12 exhibited the same crystalline structure as that during the heating process. The crystalline structure of PAPACM12 was attributed to α-form crystal, which is the stable form, according to the WAXD diffraction peaks of the conventional AABB-type polyamides. During stretching deformation, the crystal transition from α-form to γ-form and strain-induced crystallization were observed to contribute to the PAPACM12 with higher breaking strength and elongation. This study firstly determine the crystalline structure of transparent polyamides, and then the controlled strain-induced crystallization and transformation are demonstrated to be effective preparation methods for polyamides with high properties. [ABSTRACT FROM AUTHOR]

In this work, the crystallization kinetics of poly(ethylene oxide) (PEO) matrix included with poly(ethylene glycol) (PEG) grafted silica (PEG-g-SiO2) nanoparticles and bare SiO2 were systematically investigated by differential scanning calorimetry (DSC) and polarized light optical microscopy (PLOM) method. PEG-g-SiO2 can significantly increase the crystallinity and crystallization temperature of PEO matrix under the non-isothermal crystallization process. Pronounced effects of PEG-g-SiO2 on the crystalline morphology and crystallization rate of PEO were further characterized by employing spherulitic morphological observation and isothermal crystallization kinetics analysis. In contrast to the bare SiO2, PEG-g-SiO2 can be well dispersed in PEO matrix at low P/N (P: Molecular weight of matrix chains, N: Molecular weight of grafted chains), which is a key factor to enhance the primary nucleation rate. In particular, we found that the addition of PEG-g-SiO2 slows the spherulitic growth fronts compared to the neat PEO. It is speculated that the interfacial structure of the grafted PEG plays a key role in the formation of nuclei sites, thus ultimately determines the crystallization behavior of PEO PNCs and enhances the overall crystallization rate of the PEO nanocomposites. [ABSTRACT FROM AUTHOR]

Crossover of mesophase to crystalline structure in the nanoconfinement crystallization process of frustrated side groups elucidates the critical crystal thickness dcor the length scale of side groups, which defines the transition process from mesophase (hexagonal and monoclinic phase) to crystalline phase (orthorhombic phase) of confined CH2sequences in a given crystal size restriction. [ABSTRACT FROM AUTHOR]

The morphology, crystallization behavior, and properties of multi‐crystalline polymer systems based on triple crystalline biodegradable PEO‐b‐PCL‐b‐PLLA triblock terpolymers are reviewed. The triblock terpolymers, with increasing poly(l‐lactide) (PLLA) content, exhibit a triple crystalline nature. Upon cooling from melt, the PLLA block crystallizes first and templates the spherulitic morphology of the terpolymer. Then, the poly(ε‐caprolactone) (PCL) block crystalizes and, finally, the poly(ethylene oxide) (PEO) block. These triblock terpolymers are melt miscible according to small angle X‐ray scattering (SAXS) results. Thus, the crystallization of PCL and PEO blocks takes place within the interlamellar zones of the PLLA spherulites that are formed previously. Therefore, the lamellae of PLLA, PCL, and PEO exist side‐by‐side within a unique spherulite, constituting a novel triple crystalline superstructure. The theoretical analysis of SAXS curves implies that only one lamella of either PCL or PEO can occupy the interlamellar space in between two contiguous lamellae of PLLA. Several complex competitive effects such as plasticizing, nucleation, anti‐plasticizing, and confinement take place during the isothermal crystallization of each block in the terpolymers. New results on how successive self‐nucleation and annealing thermal treatment can be used as an additional suitable technique to properly separate the three crystalline phases in these triple crystalline triblock terpolymers are also included. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A disulfide‐based poly(ether‐b‐amide) copolymer with rapid self‐healing capability under moderate conditions was synthesized from 4,4'‐dithiodibutyric acid (DTDBA), isophorondiamine (IPDA) and poly(tetramethylene oxide) (PTMO) based on a two‐step method. The incorporation of IPDA with asymmetric structure and substantial steric hindrance not only effectively decreased the number of regular H‐bonds, but also inhibited the crystallization of polyamide segments, imparting the synthesized poly(ether‐b‐amide) copolymer with an amorphous structural feature. Based on the coordination of segmental diffusion and recombination of disulfide bonds and hydrogen bonds, the scratches and damaged mechanical properties of PEBADS‐I611 could be completely self‐healed after healing at 40 °C for only 11 min and 3 h, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The shear-induced crystallization behavior of isotactic polypropylene (i-PP) has been investigated by in situ optical microscope under various thermal and shear histories. A shish-kebab structure during growth was observed under a well controlled, however, weak shear field. According to our results under these weak shear and thermal history, a modified model was proposed for the growing process of melt shear-induced crystallization of i-PP. Furthermore, many physical insights were provided on several still unsettled issues such as extended chain crystals, row nuclei, and smectic ordering questions. [Copyright &y& Elsevier]

Abstract Observations of large property changes in the presence of nanoparticles have motivated an increasing interest towards the interfacial effect in polymer nanocomposites. In this work, the interface between poly(ethylene oxide) (PEO) and silica (SiO 2) was modulated by the inclusion of SiO 2 with three different surface functionalities, namely unfunctionalized SiO 2 (SiO 2 -OH, grafting density = 0 chains/nm2), PEO-grafted SiO 2 , SiO 2 - g -PEO-1.1 (grafting density = 1.1 chains/nm2) and SiO 2 - g -PEO-2.2 (grafting density = 2.2 chains/nm2), and the interfacial effect on crystallization behavior of PEO/SiO 2 nanocomposites was studied by the combination of differential scanning calorimetry (DSC) and polarized light optical microscopy (PLOM) analysis. In contrast to the unfunctionalized SiO 2 , PEO grafting imparts SiO 2 with a high nucleation ability, even though SiO 2 -OH demonstrates more homogenous dispersion in PEO matrix than PEO-grafted SiO 2. The overall crystallization rate of PEO/SiO 2 nanocomposites follows the order PEO/SiO 2 - g -PEO-2.2 > PEO/SiO 2 - g -PEO-1.1 > PEO/SiO 2 -OH. These results highlight the role of grafted chains on crystallization. It is speculated that the interfacial structure, as a function of grafting density, plays a critical role in the formation of nuclei, which ultimately determines the crystallization behavior. This work can contribute to understanding the interfacial effect in polymer nanocomposites and is believed to provide theoretical guidance for manipulating the properties of materials. Graphical abstract Image 1 Highlights • A marked enhancement in the crystallization rate of PEO with the inclusion of the PEO-grafted SiO 2 nanoparticles. • Increased nucleation power of PEO-grafted SiO 2 nanoparticles with the grafting density. • Well-illustrated interfacial structures as a function of grafting density. • Highlighting the role of grafted chains on crystallization. • Correlating the interfacial structures with the crystallization of polymer nanocomposites. [ABSTRACT FROM AUTHOR]

The random incorporation of comonomer units in isotactic polypropylene usually disrupts the chemical regularity of the macromolecular chain, thereby remarkably affecting the crystallization and melting processes. We study the influence of a novel comonomer 4-(7-Octen-1-yl)- N , N -diphenylaniline (ODPA), in the concentration range of 1.1–6.8 mol%, on the crystallization and self-nucleation behavior of isotactic polypropylene copolymers. Non-isothermal and isothermal differential scanning calorimetry experiments demonstrated that crystallization kinetics are significantly retarded upon comonomer incorporation as the ODPA co-units are excluded to the amorphous regions. Furthermore, ODPA comonomer incorporation leads to a sharp increase in nucleation density; thus, spherulitic superstructures become significantly smaller. Remarkably, the ODPA co-units induce a strong melt memory effect that can persist even above the equilibrium melting temperature for copolymers with 4.4–6.8 mol% ODPA. The width of Domain IIa (exclusive melt-memory domain), an indicator of the self-nucleation strength, starts to increase sharply once the content of ODPA exceeds 1.8 mol%. In contrast, the width of Domain IIb (self-seeding domain) remains constant. We attribute the self-nucleation effect in these ODPA copolymers to the aggregation of co-units in the interlamellar amorphous regions that hinder, upon melting, the motion of the chain sequences that were initially packed within the crystal lattice. In this way, to reach the isotropic melt state, the sample must be heated to much higher temperatures than its apparent or even equilibrium melting point, depending on the comonomer content. Consequently, nucleation upon cooling from the self-nucleated melt becomes easier and faster. [Display omitted] • 4-(7-Octen-1-yl)- N,N -diphenylaniline counits strengthen melt memory in PP copolymers. • Melt memory strongly increases with ODPA incorporation above a critical concentration. • For copolymers with 4.4–6.8 mol% ODPA, melt memory persists even above T m 0 . [ABSTRACT FROM AUTHOR]

The formation of trigonal Form I′ crystals of polybutene-1 (PB-1) directly from melt has drawn much attention in past decades. In this study, we investigate the fractionated crystallization behavior of PB-1 within droplets formed by blending PB-1 with an excess of isotactic polypropylene (iPP) employing DSC, SEM, in situ synchrotron WAXD and FT-IR. When PB-1 is dispersed into a large number of small size droplets, the heterogeneous nucleation of Form II crystals can be inhibited because the number of droplets is larger than that of active nucleation sites for Form II (i.e., active heterogeneities originally present in bulk PB-1). The nucleation of the finely dispersed PB-1 droplets does not occur homogenously, but at the interface with the iPP matrix, which induces the crystallization of the droplets into Form I′. The crystallization rate of Form I′ at different temperatures was determined by Fourier transform infrared spectroscopy. It was found that trigonal Form I′ crystallizes faster when the content of PB-1 in the blend is lower, and the specific interfacial surface area is larger. The opposite effect has been observed for the kinetics of the metastable Form II formation. It is therefore suggested that Form I′ crystallization is driven by the nucleation of PB-1 at the crystalline iPP surface, which competes with the crystallization of Form II induced by nucleating heterogeneities present in PB-1 droplets. [ABSTRACT FROM AUTHOR]

The structure evolution of poly(3-dodecylthiophene) (P3DDT) during heating was investigated by differential scanning calorimetry (DSC) and in-situ wide and small-angle X-ray scattering (WAXS/SAXS). Four regions were classified in the heating process, i.e. below the melting temperature of the side chain (I), side-chain melting region (II), below main chain melting region (III) and the melting of the main chain region (IV). Melting of side chains in region II introduced an expansion of the (1 0 0) plane spacing, resulting in a lower crystalline phase density and therefore a lower crystalline/amorphous density contrast. The reorganization process during heating was observed. The double melting peaks during heating were shown to result from melting and recrystallization. No evidence of liquid crystalline phase or mesophase was observed above the melting temperature of P3DDT. [ABSTRACT FROM AUTHOR]

A new kind of elastic filament fibers based on long chain poly(amide-block-ether) (LPAE) was successfully prepared by simple melt spinning. The LPAE elastomer was synthesized with hard blocks of long chain polyamide (LCPA) oligomers, produced by bio-fermenting monomers, and poly(tetra-methylene ether) glycol (PTMEG) soft blocks. The mechanical and thermal results demonstrated that it represented large elongation at break, low initial modulus and excellent elastic recovery, which were comparable to that of commercially used spandex within strain of 200% and superior to that of olefin-based XLA fibers. The high elasticity and reversibility arise from that the LCPA hard segments, representing semi-crystalline state at ambient temperature and generating three dimensional hydrogen bonds between adjacent chains, serve as the physical crossing linking sites, while the polyether soft segments can be deformed largely due to amorphous state and the easy conformation changes of polymer chains. However, beyond 200%, the recovery gradually drops and it origins from the strain-induced crystallization and slight crystal transition in soft and hard segments, respectively. Hence, the novel elastic filament fibers retain the merits of the segmented copolymer and LCPA like better dimensional stability, chemical and abrasion resistance, and better soft handle. With this research, LPAE elastic fiber, featuring excellent elasticity and reversibility, is confirmed to be a promising candidate to replace spandex and XLA fibers in some typical textile applications. [ABSTRACT FROM AUTHOR]

The isothermal crystallization behavior of a 1:1 poly( l -lactide)/poly( d -lactide) (PLLA/PDLA) mixture under pulsed shear was investigated by in-situ polarized light optical microscopy (POM) and wide angle X-ray scattering (WAXS). The effects of shear rate and temperature were studied. The results showed that application of shear flow increased the nucleation density, crystallization rate and degree of orientation for both stereocomplex crystals (SC) and α crystals. Interestingly, when the crystallization temperature was below the melting temperature of α crystals, the phase content of SC increased with shear rate, while the α content displayed a bell-shaped curve with regard to shear rate. The structure formation in this system was closely related to the shear-induced nucleation, phase mixing and chain mobility. [ABSTRACT FROM AUTHOR]

An aryl amide derivative (TMB-5) was used to nucleate the poly( l -lactide)/poly( d -lactide) (PLLA/PDLA) blend for the first time. The effect of TMB-5 nucleating agent on the crystallization behavior of PLLA/PDLA blend was systematically investigated. The selective nucleation of stereocomplex (sc) crystals by incorporation of TMB-5 was realized under appropriate crystallization conditions. During the cooling process, various morphology of TMB-5 due to its partial or complete dissolution in the PLLA/PDLA blend melt was observed. Furthermore, an sc crystals layer on the lateral surface of TMB-5 was found. Upon cooling a PLLA/PDLA blend from 260 °C at rates between 2 and 100 °C/min, 0.5 wt% addition of TMB-5 induced a single melting peak of sc crystals and no homocrystallization was observed in the subsequent DSC heating scan. The melting temperature of the sc crystals was found to decrease in the presence of TMB-5 from 230 to ca. 200 °C, which is still 20 °C higher than that of PLLA homopolymer. The results suggest that the supramolecular structure of the nucleating agent plays an important role in the crystallization of the PLLA/PDLA blend. The difference in solubility and recrystallization ability of TMB-5 in polymer melt results in the variation of crystallization behavior of PLLA/PDLA blend, which is correlated with the concentration of TMB-5 and crystallization conditions including the final melting temperature, annealing time and cooling rate. [ABSTRACT FROM AUTHOR]

Poly (butylene succinate) (PBS) and polycaprolactone (PCL) are two immiscible biocompatible and biodegradable polymers. Aiming to combine the properties of these biodegradable polymers, this work explores for the first time blending PBS or PCL with PBS- ran -PCL copolymers (BS x CL y) at 75/25, 50/50, and 25/75 wt% compositions, with various copolymer contents: BS 78 CL 22 , BS 46 CL 54 , and BS 15 CL 85. The crystallization behavior of these novel binary blends was systematically studied with non-isothermal and isothermal differential scanning calorimetry (DSC), polarized light optical microscopy (PLOM), and simultaneous wide- and small-angle X-ray scattering (WAXS and SAXS). All the blends displayed a miscible character in the amorphous state, judging by a single glass transition temperature, and in the melt state (as indicated by SAXS), but their miscibility in the crystalline state depends on the specific blend. In both PBS/BS 78 CL 22 and PCL/BS 15 CL 85 evidences of co-crystallization between the matrix and the crystallizable fraction of the copolymer were found. However, high comonomer exclusion, higher in the BS 15 CL 85 than in the BS 78 CL 22 , greatly affects blend miscibility. Thus, the results show that the PBS/BS 78 CL 22 blend is miscible, in the crystalline state, at high PBS (homopolymer) content, i.e., 75/25 and 50/50 compositions, whereas its "counterpart", the PCL/BS 15 CL 85 displays partial miscibility, even for high PCL (homopolymer) content. For the 25/75 blends, i.e., copolymer-rich, the homopolymer addition favors the crystallization of the copolymer-rich component. Blending PBS or PCL with BS 46 CL 54 leads to blends that exhibit a much lower miscibility in the crystalline state than the blends prepared with BS or CL-rich copolymers, independently of the composition. But, interestingly, a novel behavior is found, since the BS 46 CL 54 copolymer can crystallize either in PBS type crystals or in PCL type crystals depending on the polymeric matrix (PCL or PBS). The PBS favors the crystallization of the BS component, while the PCL favors the crystallization of the CL component within the random copolymer. The crystallization behavior found in this work evidences the interactions of the PBS or PCL with the BS x CL y copolymer, representing a potential strategy to combine the properties of the PBS and PCL through blending. [Display omitted] • Combining properties of PBS and PCL by blending with their BS x CL y copolymers. • Novel binary blends of PBS or PCL with BS x CL y copolymers in various compositions. • Influence of the polymeric matrix on the BS 46 CL 54 crystallization. • How exclusion/inclusion balance affects matrix - BS x CL y copolymer interactions. • Tailoring properties of biodegradable binary blends: blend components and ratio. [ABSTRACT FROM AUTHOR]

The present work deals with the flow-induced multiple orientations and crystallization structure of polymer melts under a complex flow field. This complex flow field is characteristic of the consistent coupling of extensional “pulse” and closely followed shear flow in a narrow channel. Utilizing an ingenious combination of an advanced micro-injection device and long chain aliphatic polyamides (LCPA), the flow-induced crystallization morphology was well preserved for ex-situ synchrotron micro-focused wide angle X-ray scattering (μWAXS) as well as small angle X-ray scattering (SAXS). An inverted anisotropic crystallization structure was observed in two directions: perpendicular and parallel to the flow direction (FD). The novel anisotropic morphology implies the occurrence of wall slip and “global” fountain flow under the complex flow field. The mechanism of structure formation is elucidated in detail. The experimental results clearly indicate that the effect of extensional pulse on the polymer melt is restrained and further diminished due to either the transverse tumble of fountain flow or the rapid retraction of stretched high molecular weight tails. However, the residual shish-kebab structures in the core layer of the far-end of channel suggest that the effect of extensional pulse should be considered in the small-scaled geometries or under the high strain rate condition. [ABSTRACT FROM AUTHOR]

The non-isothermal crystallization behavior of poly( l -lactide)/poly( d -lactide) (PLLA/PDLA) blends under shear was investigated by in-situ polarized light optical microscopy (POM) and wide angle X-ray scattering (WAXS). Pulse shear for 5 seconds was applied to the melt during cooling. The effects of shear temperature and shear rate were systematically studied. It was found that the shear field could increase the nucleation density of stereocomplex crystal (SC), and accelerate the overall crystallization rate. The final crystallinity of SC increased to as high as ∼45% with a shear rate of 178 s −1 when the shear temperature was 150 °C. The onset crystallization temperature of α crystals increased by ∼10 °C. The final content of α crystals reduced with the increase of SC content. Multiple factors influence the crystallization of SC and α crystals, including the shear rate, shear temperature and the nucleating/confinement effect of SC on α crystals. [ABSTRACT FROM AUTHOR]

A novel strategy for preparation of unsaturated polyester-based functional materials with widely tunable mechanical properties has been reported in present work. The biodegradable and crystallizable poly(butylene fumarate) oligomer (PBF) bearing reactive carbon–carbon double bonds on the backbone was functionalized by Michael addition with furfurylamine (FA), followed by incorporating bismaleimide (BMI) as cross-linker to form a reversibly cross-linked polyester (PBF-FA-BMI). The obtained material was systematically characterized by a combination of differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), rheometry measurement, wide-angle X-ray scattering (WAXS) as well as mechanical property testing. The in-situ FTIR and rheology measurements demonstrated the competition process of DA reaction and crystallization for dynamic conditions and isothermal conditions. The characteristic of dynamically chemical structure variation and crystallization behavior provides a possibility to tune the mechanical property of PBF-FA-BMI. By thermal treatment, the structure programming of the material can be facilely achieved, which undergoes from a typically elastomer to plastic. A schematic illustration of thermo-responsive conversion and recyclability is proposed for the cross-linked polyester. [ABSTRACT FROM AUTHOR]

This work examined the effect of nucleating agents on the strain-induced crystallization of poly( l -lactide) (PLLA). Talc and poly( d -lactide) (PDLA) were used as the nucleating agents of PLLA. Wide angle X-ray scattering (WAXS) revealed that the original injection molded specimens of nucleated PLLA blends were free of PLLA α crystal. The structural evolution during uniaxial stretching of neat and nucleated PLLA above the glass transition temperature was investigated by in-situ WAXS. It was observed that the nucleating agents significantly accelerated the crystallization of PLLA during stretching. The accelerating effect for the PLLA crystallization during stretching increased in the following order: PDLA/talc > PDLA > talc. In step-strain measurements with a high stretching speed, the effect of nucleating agents on the crystallization of PLLA showed a strain-dependence. The enhancement of crystallization by nucleating agents was remarkable at 200% strain. However, with 500% strain, the strain-induced crystallization was dominant and the effect of nucleating agents on crystallization of PLLA was not obvious. The results were analyzed considering the nucleating effect of nucleating agents on PLLA. [ABSTRACT FROM AUTHOR]

Motivatedby the interest in an interfacial effect on crystallizationbehaviors and material properties of polymer nanocomposites, phasebehaviors of a novel model system for polymer nanocomposite, 1-octadecanol/silicananosphere composites (C18OH/SiO2), were studiedby means of thermal analysis and wide-angle X-ray diffraction. Althougha huge specific surface area of silica nanoparticles enlarges thesurface–volume ratio of C18OH molecules, surfacefreezing phenomenon is not observed by DSC in the C18OH/SiO2composites. While pure C18OH exhibits rotatorRIVphase with molecules tilted with respect to the layernormal, the silica network favors and enhances untitled RIIphase by disturbing the layering arrangement. Moreover, the confinedC18OH shows a polycrystalline mixture of orthorhombic βform and monoclinic γ form. It is demonstrated that the interfacialinteraction between the C18OH molecules and the silicasurface contributes to the peculiar phase transition behaviors ofC18OH/SiO2composites. The investigation ofthe model system of long-chain alcohol/nano-SiO2compositesmay help us to understand the complicated interfacial effect on phasebehaviors and material properties of polymer nanocomposite systems. [ABSTRACT FROM AUTHOR]

The confined phase behaviors of microencapsulatednormal hexadecane/octadecanemixtures (abbreviated as m-C16/C18) have been investigated by combination of differential scanningcalorimetry and in situwide-angle X-ray scattering.The binary alkane mixtures confined in three-dimensional geometricalspace demonstrate two novel crystallization features. The surfacefreezing is significantly enhanced after C16/C18mixtures being encapsulated, and the surface monolayer formed isproved to be an ideal solid solution composed by C16andC18. Furthermore, m-C16/C18mixtures are trapped into a stabilized rotator phase belowthe crystallization temperatures, whereas C16/C18mixtures with certain compositions form the low-temperature crystallinestructure directly. These confined crystallization features originatefrom the jointed effects of spatial confinement and chain mixing ofthe components. Moreover, the phase diagram of the confined binaryalkane mixtures (m-C16/C18)is successfully established for the first time, which enlightens thecrystallization features of other spatially confined soft-matter binarysystems. [ABSTRACT FROM AUTHOR]

There has been considerable interest in the nucleation and crystallization of polymers in the presence of nanoparticles (NPs, or nanofillers in general, NFs). Most of the extensive work in this area has focused on anisotropic, non-Brownian NFs (e.g., clay sheets, carbon nanotubes) whose spatial dispersion state in these nanocomposites is controlled by the process by which they are formed. Hence, NF spatial dispersion is generally limited and often remains poorly characterized. Thermodynamic handles that can be used to control NF dispersion state in the polymer melt include (a) favorable interactions between the polymer chains and the bare NP surfaces, or (b) the density and length of the chains, with the same chemistry as the matrix, grafted to the NP surface. These relatively large NFs merely act as stationary objects that affect the kinetics of nucleation by providing heterogeneous sites, and the crystallization rate by confining the polymer in the melt state. The dispersion state of the NFs can dramatically affect the nucleation and crystallization of the matrix, but in most cases reported, the NFs increase nucleation efficiency relative to the neat polymer. At higher NF loadings, the effect of polymer confinement by the NFs dominates, leading to a decrease in crystal growth rates. This review describes the most important lessons learned from these commonly studied systems and then extends to polymer composite systems containing small, mobile spherical NPs (typically smaller than 100 nm in size). The role of NP mobility, which provides for dynamic confinement of the polymer melt, on the kinetics of polymer crystallization (nucleation, growth, and overall crystallization) and how this behavior is mostly consistent with the case of immobile NF is a second important focus of this review. In addition to the role of NFs on crystallization kinetics, recently reported nanoparticle ordering phenomena such as the effect of matrix crystallization on the organization of small spherical NPs within the amorphous regions of the semicrystalline morphology are discussed. Such phenomena are clearly not observed for large NFs and hence provide a point of departure from past works in this area. [Display omitted] [ABSTRACT FROM AUTHOR]

How polymers crystallize can greatly affect their thermal and mechanical properties, which influence the practical applications of these materials. Polymeric materials, such as block copolymers, graft polymers, and polymer blends, have complex molecular structures. Due to the multiple hierarchical structures and different size domains in polymer systems, confined hard environments for polymer crystallization exist widely in these materials. The confined geometry is closely related to both the phase metastability and lifetime of polymer. This affects the phase miscibility, microphase separation, and crystallization behaviors and determines both the performance of polymer materials and how easily these materials can be processed. Furthermore, the size effect of metastable states needs to be clarified in polymers. However, scientists find it difficult to propose a quantitative formula to describe the transition dynamics of metastable states in these complex systems. Normal alkanes [CnH2n+2, n-alkanes], especially linear saturated hydrocarbons, can provide a well-defined model system for studying the complex crystallization behaviors of polymer materials, surfactants, and lipids. Therefore, a deeper investigation of normal alkane phase behavior in confinement will help scientists to understand the crystalline phase transition and ultimate properties of many polymeric materials, especially polyolefins. [ABSTRACT FROM AUTHOR]

Abstract: The structure, porosity and crystallization behavior of poly (L-lactic acid) and poly (L-lactic acid)/polyurethane porous membranes, prepared from ethanol/dioxane and ethanol/water coagulation baths through immersion precipitation, have been systematically investigated. The diffusion rate between solvent and nonsolvent as well as the equilibrium phase diagram of PLLA/solvent/nonsolvent system were also well studied. It has been proved that the ultimate structure and performance of the membranes could be mediated under control by suitable adjustment on phase separation behavior of the ternary system through varying coagulation bath compositions. The results show that the presence of lower ratio of dioxane in ethanol baths endows the resulting membranes with uniform sponge-like structure, higher porosity and crystallinity due to the moderate solidification and crystallization of PLLA, while increasing the water concentration tends to have a modestly opposite effect and obtains membranes with irregular finger-like structure, lower porosity and crystallinity. Under the same coagulation baths, PLLA/PU membranes possess slightly larger pores size and porosity than pure PLLA membranes, but the presence of PU appears to have no effect on the crystallinity of PLLA. [Copyright &y& Elsevier]

Crystallization and phase transitionbehaviors of n-hexadecane (n-C16H34, abbreviatedas C16) confined in microcapsules and n-alkane/SiO2nanosphere composites have been investigatedby the combination of differential scanning calorimetry (DSC) andtemperature-dependent X-ray diffraction (XRD). As evident from theDSC measurement, the surface freezing phenomenon of C16is enhanced in both the microcapsules and SiO2nanospherecomposites because the surface-to-volume ratio is dramatically enlargedin both kinds of confinement. It is revealed from the XRD resultsthat the novel solid–solid phase transition is observed onlyin the microencapsulated C16, which crystallizes into astable triclinic phase via a mestastable rotator phase (RI). For theC16/SiO2composite, however, no novel rotatorphase emerges during the cooling process, and C16crystallizesinto a stable triclinic phase directly from the liquid state. Heterogeneousnucleation induced by the surface freezing phase is dominant in themicroencapsulated sample and contributes to the emergence of the novelrotator phase, whereas heterogeneous nucleation induced by foreigncrystallization nuclei dominates the C16/SiO2composite, leading to phase transition behaviors similar to thoseof bulk C16. [ABSTRACT FROM AUTHOR]

Abstract: The growth of transcrystallites induced by fracture stress was studied in the solution casted polystyrene (PS)/poly(ethylene oxide) (PEO) blends films. Both the structure geometry of the crack edge and the effect of local fracture stress on the crystallization were considered. It was found that the local fracture stress contribution is the most important factor to the formation of transcrystallites. Transcrystallites were obtained when PEO crystallized before the local fracture stress was relaxed, while only regular spherulites were obtained when crystallization took place after the relaxation of the local fracture stress. [Copyright &y& Elsevier]

Abstract: Two kinds of low molecular weight aliphatic amides, N, N′-ethylenebis (12-hydroxystearamide) (EBH) and N, N′-ethylenebisstearamide (EBSA), have been selected in present study to mediate the crystallization behavior of poly (L-lactic acid) (PLLA). The results showed that the crystallization rate of PLLA was significantly improved with the addition of EBH and EBSA, and EBH presented a stronger nucleating efficiency. The correlation between the variation of chain conformation during the early stages of isothermal crystallization and the enhancement of crystallization rate for pure PLLA and its mixtures was investigated by time-resolved FTIR. The formation of interchain conformational-ordered structure and intrachain 103 helix structure for amide-doped PLLA preceded that for pure PLLA, suggesting a stimulatory nucleating effect of EBH and EBSA. In the case of PLLA/EBH, the interchain interactions of –(COC + CH3) and –CH3 groups were faster than the –(CH3+CC) intrachain interactions, while the interchain interactions and the intrachain 103 helix formation were nearly synchronous for PLLA/EBSA. The hydrogen bond interaction between hydroxyl groups in EBH and the carbonyl groups in PLLA was proposed to be an important factor influencing the conformation variation during isothermal crystallization of PLLA. [Copyright &y& Elsevier]

Abstract: Calcium oxalate particles with different morphologies and phase structures were prepared by a facile precipitation reaction of sodium oxalate with calcium chloride in the presence of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) at different temperatures. The as-prepared products were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the variations in the concentration of surfactants and temperatures significantly influenced the crystal structure, morphology, and particle size of the products. Cationic surfactant CTAB did not affect the crystal phase: calcium oxalate monohydrate (COM) was the only hydrate formed. Anionic surfactant SDS, however, not only changed the crystal shape, but also induced the formation of metastable calcium oxalate dihydrate (COD) with increasing surfactant concentration. High temperature favored the formation of COM. This work may provide new insights into the morphological control of calcium oxalate particles. [Copyright &y& Elsevier]