Crystalline structure and morphology of poly(L‐lactide) formed under high pressure

The poly(l ‐lactide) (PLLA) samples were prepared by the annealing under 100 MPa at 75–145^°C and 200 MPa at 105–145^°C for 6 h, respectively. The crystalline structures, thermal properties and morphology were investigated using differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and scanning electron microscopy (SEM). On the basis of the DSC and WAXD results, it can be seen that the α′ form was formed by the annealing under 100 MPa at 85–95°C but not found under 200 MPa at 105–145°C. A phase diagram of PLLA crystal form under high pressure was constructed under the given experimental conditions, which displayed the α′ form was formed at limited temperature and pressure range. Besides, SEM suggested that the PLLA samples annealed under 100 MPa crystallize to form lamellar‐like crystals due to the low growth rate and the confined crystallization behavior under high pressure. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40637.     

Hemodialysis membranes prepared from poly(vinyl alcohol): Effects of the preparation conditions on the morphology and performance

Poly(vinyl alcohol) was employed for the preparation of hemodialysis membranes with and without the addition of acetic acid and poly(ethylene glycol) with the phase‐inversion process. Aqueous solutions of sodium sulfate and sodium hydroxide were chosen as coagulant baths. The performances of the membranes were estimated by the measurement of the removal of uremic toxins (urea, uric acid, and creatinine) from human blood serum. The morphologies of the membranes were investigated and correlated to the membrane performance. Increasing the poly(ethylene glycol) concentration in the polymer solutions resulted in porous, spongelike structures because of the higher polarity of the polymer solutions and the enhancement of the diffusion rate of the nonsolvent (sodium sulfate and sodium hydroxide) into the polymer solutions. The porous structures of the membranes enhanced the removal of uremic toxins. The presence of acetic acid, with greater ionization strength, resulted in higher electrostatic interactions between positive and negative ions in the coagulation baths and polymer solutions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2490–2497, 2007     

PET-PTMG聚醚酯熔融与结晶行为的研究

采用熔融缩聚法合成了一系列聚对苯二甲酸乙二醇酯(PET)-四氢呋喃聚醚(PTMG)聚醚酯，用DSC、偏光显微镜表征了材料的熔融与结晶性能，讨论了组成对聚醚酯的熔点、结晶温度、结晶度、结晶形态的影响。结果表明，PET—PTMG聚醚酯的熔点与组成的关系符合Baur公式；其结晶度随着聚醚含量的增加呈现先升高后下降的趋势；并为明显的结晶与非结晶的两相结构形态。     

Poly(caprolactone) thin film preparation,morphology, and surface texture

The properties and surface uniformity of poly‐ (caprolactone) (PCL) thin films were measured. Thin films were prepared using a spin‐coating technique. Film thickness and roughness were correlated with variation in solution concentration, spinning speed and spinning time. Differential scanning calorimetry (DSC) was used to investigate the crystallization and melting processes. The enthalpy of melting variation correlated with the film thickness, while melting temperature was independent of film thickness. In addition, surface roughness was found to be a function of PCL thickness. Film thickness and roughness showed a progressive decrease when spinning speed was increased, while spinning time provided no significant influence on film thickness. PCL thickness and roughness significantly increased when PCL solution concentration increased. Hot stage optical microscopy showed that larger spherulitic crystals were present in thin films, and the smaller crystals present in thicker films had a coarser texture consistent with increased surface roughness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1287–1294, 2007     

聚乳酸结晶的研究进展

综述了自合成以来聚乳酸（PLA）结晶行为研究的主要成果，介绍了PLA的α、β、γ三种晶型结构参数及不同晶型晶体的形成条件，以及PLA球晶、单晶、孪晶、微纤晶和串晶等结晶形态及其形成条件。此外，还介绍了PLA在不同条件下的结晶行为，着重阐述了分子结构、第二组分及温度场、应力场以及辐照等外部因素对其结晶行为的影响。     

锚定的磷脂双层膜的制备及其形貌结构

利用表面硅烷化方法对化学氧化的单晶硅表面进行修饰,成功地将抗生物素蛋白固定在表面上,并且用囊泡融合法成功得到了大面积、连续的磷脂双层膜。由于成功地在基底与磷脂膜间引入了5nm左右的水层,原子力显微镜观察表明这种锚定的磷脂双层膜(tethered bilayer lipid membrane, tBLM)表现出与磷脂支持膜不同的相形为。两种膜相形为的不同可以用磷脂分子与基底间相互作用的不同来解释。     

Melt Crystallization Behavior and Spherulitic Morphology of Poly(Trimethylene Terephthalate)/Poly(Propylene Glycol) Copolymers with Different Poly(Propylene Glycol) Molecular Weights

Poly(trimethylene terephthalate)/poly(propylene glycol) (PTT/PPG) copolymers with different PPG molecular weights (400–4,000?g?/mol) were successfully synthesized and characterized. Double melting endotherms during isothermal melt crystallization were observed by differential scanning calorimetry. Middle-temperature melting endotherms in all copolymers were stronger than that in PTT homopolymer and became smaller with the increasing PPG molecular weight. Nonisothermal crystallization kinetics of all samples were analyzed by Ozawa and Mo models. Polarized optical microscopy micrographs revealed that ring-banded spherulitic morphology was relatively easier to be observed in copolymers with higher PPG molecular weight at lower crystallization temperature, and PPG molecular weight nearly had no influence on the band spacing.     

Poly(1,4-trans-cyclohexanediyldimethylene adipate): Polymorphism and the structure of form I,using X-ray diffraction

Poly(1,4-trans-cyclohexanediyldimethylene adipate) or poly(t-CDA) crystallizes in two forms. Form I of poly(t-CDA) is analogous to the one reported for poly(t-CDS). Poly(t-CDA) has a monoclinic unit-cell of dimensions a = 6.938, b = 9.761, $\text{c = 15.97}\text{A}\text{?}$ and β = 41.4° and belongs to the $\text{P2}{}_1\text{n}$ space group. The calculated crystalline density of 1.181 g cm^?3 indicates that there is one chemical unit per fibre-repeat and two chains per unit-cell. The crystal structure of poly(t-CDA), form I was established using published structural data on related molecules for model building combined with a packing minimization procedure. The structure was confirmed by a comparison of calculated and observed structure amplitudes derived from an X-ray fibre diagram. The agreement index wR has the value of 0.153 for 31 observed diffraction data. The OCH₂(C₆H₁₀)CH₂O moiety of the polyester has the conformation t²_g(tg±t)^g?_tg (g, gauche and t, trans), while the adipate group is in the trans conformation. From II of poly(t-CDA) was identified through its distinct X-ray diffraction pattern, but its structure has not yet been established.     

Development of novel biocomposites based on the clean production of microbial cellulose from dairy waste (sour whey)

This work explores the production of kombucha-derived bacterial cellulose (KBC) from sour whey via the fermentation method using Komagatacibacter xylinus. The biosynthesis process was optimized by design of experiments and the results displayed highest KBC yield at 1000 ml/L sour whey waste, 87.39 g/L cane sugar, 6 g/L black tea, and 78.91 ml/L bacteria volume under 21 days culture period at 30°C. Optimum fermentation batch efficiency was achieved in large scale with cultured medium depths of 0.5 cm and low-residual bacteria suspension volume of 72.31 ± 8.74 ml. The obtained KBC membranes were analyzed by SEM, FTIR, XRD, and TGA. The obtained results show no significant differences for all prepared KBC samples when compared to pristine bacterial cellulose from standard Hestrin and Schramm (HS) medium. In addition, the optimized KBC was investigated as a suitable bio-filler in the preparation of biocomposite materials. The prepared biocomposites as leather alternative were further characterized and their mechanical tensile strength and elongation at break determined in the range of 135.61 ± 9.15 to 154.89 ± 9.09 N/mm² and 31.06 ± 0.32 to 92.33 ± 6.91%, respectively. This model obtained depicts high-yield production of KBC and its potential in the preparation of biocomposites.     

Spherulite morphology and crystallization behavior of poly(trimethylene terephthalate)/poly(ether imide) blends

The spherulite morphology and crystallization behavior of poly(trimethylene terephthalate) (PTT)/poly(ether imide) (PEI) blends were investigated with optical microscopy (OM), small-angle light scattering (SALS), and small-angle X-ray scattering (SAXS). Thermal analysis showed that PTT and PEI were miscible in the melt over the entire composition range. The addition of PEI depressed the overall crystallization rate of PTT and affected the texture of spherulites but did not alter the mechanism of crystal growth. When a 50/50 blend was melt-crystallized at 180 °C, the highly birefringent spherulite appeared at the early stage of crystallization (t < 20 min). After longer times, the spherulite of a second form was developed, which exhibited lower birefringence. The SALS results suggested that the observed birefringence change along the radial direction of the spherulite was mainly due to an increase in the orientation fluctuation of the growing crystals as the radius of spherulite increased. The lamellar morphological parameters were evaluated by a one-dimensional correlation function analysis. The amorphous layer thickness showed little dependence on the PEI concentration, indicating that the noncrystallizable PEI component resided primarily in the interfibrillar regions of the growing spherulites.     

Crystalline structure of poly(hexamethylene succinate) and single crystal degradation studies

The morphology of solution grown single crystals of poly(hexamethylene succinate) (PE 6 4) was investigated using dilute alcohol or diol solutions by isothermal crystallization. Increasing temperatures changed the morphology of truncated rhombic crystals, which became lenticular crystals. Spiral growths and multilayered crystals as well as characteristic striations which mainly form in the {110} sectors were often observed. A regular folding surface was found by using polyethylene decoration techniques. Lamellar crystals were easily degraded with different lipases. A preferential enzymatic attack was observed to occur on the crystal edges, giving rise in some cases to highly irregular borders with a fringed texture.Lamellae gave rise to well resolved electron diffraction patterns that allowed the main packing characteristics to be determined. Fiber X-ray diffraction patterns indicate a quasi planar zig-zag conformation and a large unit cell containing eight molecular segments. This cell could not be deduced from the typical hk0 electron diffraction pattern but could be assessed from the patterns of tilted specimens.Simulation of electron diffraction patterns indicates that molecular segments are arranged with setting angles close to ±46° or ±226°. In addition, neighbouring chains along both a- and b-axis have setting angles differing by 180° in order to justify the deduced cell dimensions.     

Crystal structure of an aliphatic polyoxamide containing methyl side-groups: Poly(2-methyl-1,8-octamethyleneoxamide)

Poly (2-methyl-1,8-octametyleneoxamide) (nylon-MOMD-2) was prepared from dibutyl oxalate and 2-methyl-1,8-octamethylenediamine. The chemical structure was investigated by ¹³C nuclear magnetic resonance (¹³C NMR). The ¹³C NMR spectrum revealed that the methyl groups distribute among the four β-sites at random. The crystal structure and its temperature dependence were also investigated by molecular mechanics calculations, X-ray diffraction, and differential scanning calorimetry. The structure was determined to be monoclinic and a = 6.26 Å, b = 8.80 Å, c = 14.7 Å, and β = 50.7°. The torsion angle of the NH–CH₂ bonds has a skew conformation and there are the two distinct torsion angles in the crystal structure. The crystal structure of nylon-MOMD-2 has a disordered and statistical structure. The crystal structure shows no phase transition on heating until its melting point, although the unit cell expands in the a and b axis directions.     

塑化聚乙烯醇的流变性能及发泡行为研究

采用毛细管流变仪对PVA流变性能进行了表征,用差示扫描量热仪（DSC）研究了降温速率对PVA结晶性能的影响,通过PVA添加化学发泡剂熔融挤出的方法制备PVA发泡材料,并用扫描电镜和密度测试仪分别对发泡材料的泡孔形态和密度进行了表征。结果表明,PVA对剪切作用非常敏感,在低剪切速率下熔体粘度较大,泡孔分布均匀,材料密度较小,在高剪切作用下熔体强度低,气体容易逃逸,导致发泡材料泡孔破裂或合并;低降温速率下熔体粘度小,泡孔易合并、塌陷,合适的降温速度下,PVA熔体粘度适中,发泡材料气泡尺寸小、分布均匀,较快的降温速度下,由于气体压力过大而造成气泡合并,联通,材料密度大。     

Synthesis and characterization of a copolymer: Poly(aniline‐co‐fluoroaniline)

In the present article, we report the chemical synthesis and characterization of poly(aniline‐co‐fluoroaniline) [poly(An‐FAn)]. The copolymerization of aniline and 2‐fluoroaniline was carried out by chemical method in acidic medium. The characterization of poly(aniline‐co‐fluoroaniline) was done using FTIR, UV‐visible spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron micrography (SEM), and a four‐points‐probe conductivity method. X‐ray diffraction (XRD) and SEM characterization reveal crystalline nature of doped copolymer compared to undoped copolymer. The observed decrease in the conductivity of the copolymer relative to polyaniline is attributed to the incorporation of the fluoro moieties into the polyaniline chain. The chemically synthesized copolymer shows good solubility in common organic solvents, and is, therefore, technological useful. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1460–1466, 2001     

Poly(ether ether ketone)/poly(aryl ether sulfone) blends: Relationships between morphology and mechanical properties

Mechanical properties such as the tensile modulus, yield (break) strength, and elongation to break (or yield) are measured for multiphase poly(ether ether ketone) (PEEK)/poly(aryl ether sulfone) (PES) blends. Specimens with three different levels of thermal histories (quenched, as‐molded, and annealed) are prepared in order to study their effects on the mechanical properties of PEEK/PES blends. Synergistic behavior is observed in the tensile modulus and tensile strength of the blends in almost the whole range of compositions. The ductility of quenched blends measured as the elongation to break (yield) shows an unexpected synergistic behavior in the blend containing 90 wt % PEEK, although a negative deviation from additive behavior is observed in the rest of the compositions. A ductile–brittle transition is observed between 50 and 75 wt % PEEK in the blend. The ductile–brittle transition in as‐molded blends shifts to 75–90 wt % PEEK. Annealed blends show predominantly brittle behavior in the whole composition range. The experimental data are further correlated with the theoretically predicted results based on various composite models. Although the prediction based on these equations fails to fit the experimental data in the whole composition range, the simplex equations that are normally used for blends showing synergistic behavior produced a reasonable fit to the experimental data. The mechanical properties obtained for different blend compositions are further correlated with their morphology as observed by scanning electron microscopy. Morphological observation shows a two‐phase morphology in PES‐rich blends, which is an interlocked morphology in which the disperse phase is not clearly visible in PEEK‐rich blends, and a cocontinuous type of morphology for a 50/50 composition. Considerable permanent deformation of both the disperse and matrix phase, especially in the case of quenched tensile specimens, demonstrates the remarkable adhesion present between the two phases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2887–2905, 2003     

Minor‐phase particles evolution in a polyethylene/ethylene–propylene copolymer (80/20) blend across mixing: Breakup and coalescence

On the basis of an online sampling microscopy method, the morphological evolution of a metallocene polyethylene/metallocene ethylene–propylene copolymer system (80/20 vol %) across various mixing regimes was investigated and treated statistically. The size distributions of the minor‐phase metallocene ethylene–propylene (mEP) droplets were described with principles of irreversible thermodynamics. Such an approach allowed us to find two superimposed statistical ensembles involving primary (broken) and secondary (coalesced) mEP particles. The mean size and relative number of both broken and coalesced mEP particles were calculated. The evolution of these characteristics across melt mixing, static coalescence, and flow‐driven coalescence was analyzed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3421–3431, 2013     

Liquid phase behavior and its effect on crystalline morphology in the extruded poly(ethylene terephthalate)/poly(ethylene-2,6-naphthalate) blend

Morphology in an extruded poly(ethylene terephthalate)/poly(ethylene-2,6-naphthalate) was investigated using time-resolved light scattering, optical microscope and small-angle X-ray scattering. During annealing at 280 °C, the domain structure via spinodal decomposition preceded, the transesterification followed, and then the transesterification between the two polyesters induced the dissolution of the liquid-liquid (L-L) phase separation, i.e. the homogenization. The annealed specimen for various time periods (t_s) at 280 °C was subjected to a temperature-drop to 120 °C for the isothermal crystallization and then the effects of liquid phase morphology on crystallization was investigated. With t_s, the H_ν (cross-polarization) light scattering patterns exhibited the dramatic change from a four-leaf clover pattern with maximum intensity at azimuthal angle 45° (×-type scattering pattern) to a diffuse pattern of circular symmetry and then a four-leaf clover pattern with maximum intensity at azimuthal angles 0 and 90° (+-type scattering pattern). This suggests that the crystalline structure depends on the level of the block and/or random copolymer produced by the transesterification during annealing. The H_ν scattering patterns reflected differences in the principle polarizability of the crystalline lamellae with respect to the spherulitic radius. On the other hand, the long period L_B, an average distance between two adjacent crystalline lamellae, increased with t_s at 280 °C. The dependence of L_B on t_s was explained by the change in the crystallization rate G.     

Influence of the morphology on the fire behavior of a polycarbonate/poly(butylene terephthalate) blend

Polycarbonate/Poly(butylene terephthalate) (PC/PBT) blends are used in various industrial sectors, particularly in the cable industry. In this work, the fire behavior of PC/PBT blends was studied for the entire range of blend composition to investigate the relation between fire properties and blend morphology. The morphology of the binary blends used presents a phase inversion point for 25–30 wt % PBT. Various tests have been performed to characterize the fire behavior [limiting oxygen index (LOI), epiradiator test, cone calorimeter, and pyrolysis combustion flow calorimeter (PCFC)]. A change in fire behavior has been observed when the PBT content increases from 20 to 30 wt %, corresponding to the phase inversion, from a continuous rich-PC phase to a continuous rich-PBT phase. Consequently, it can be suggested that the control of the morphology of binary polymer blends is crucial to improve their fire properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Poly(hydroxybutyrate‐co‐hydroxyvalerate) and bovine serum albumin blend prepared by electrospinning

Electrospinning is a method for the preparation of nanosized polymer fibers. Here, electrospinning is used to prepare a blend of a polyester, poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV), and a globular protein, bovine serum albumin (BSA). The electrospun blend film is compared with a solution‐cast blend film and with single‐component electrospun films made of PHBV and BSA. In the electrospun blend films, BSA manifests itself as flat ribbons and a fine network formed from fibers less than 50 nm in diameter. The dissolution rate of BSA from the electrospun blended film is lower than from the solution‐cast one. The films are characterized using scanning electron microscopy, differential scanning calorimetry, and contact‐angle measurements. The obtained PHBV+BSA blend films have several emergent properties: a slow BSA dissolution rate, a fine BSA network, and unusual thermal behavior. Thus, the PHBV+BSA blend films introduce a new class of polymer–protein blends. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45090.     

Crystallization behavior of poly(ε-caprolactone) blocks starting from polyethylene lamellar morphology in poly(ε-caprolactone)-block-polyethylene copolymers

The crystallization behavior of poly(ε-caprolactone) (PCL) blocks starting from a solid lamellar morphology formed in advance by the crystallization of polyethylene (PE) blocks (PE lamellar morphology) in a PCL-b-PE diblock copolymer was investigated by differential scanning calorimetry (DSC), small-angle X-ray scattering with synchrotron radiation (SR-SAXS), and polarized optical microscope (POM). The crystallization behavior was quantitatively compared with that of a PCL-block-polybutadiene copolymer, where the crystallization of PCL blocks started from a rubbery lamellar microdomain. DSC and SR-SAXS results revealed that the crystallization rate of PCL blocks in PCL-b-PE increased drastically with decreasing crystallization temperature T_c and the Avrami exponent depended significantly on T_c. SR-SAXS curves during the crystallization of PCL blocks at high T_c showed a bimodal scattering character, that is, the peak position moved discontinuously with crystallization time. At low T_c, on the other hand, no shift of the SAXS peak position was observed. The macroscopic change in morphology was detected only at high T_c by POM observations. These experimental results for the crystallization behavior of PCL blocks in PCL-b-PE all support our previous conclusions obtained by static measurements; the crystallization mechanism at low T_c is completely different from that at high T_c, that is, the PCL blocks crystallize within the PE lamellar morphology at low T_c while the crystallization of PCL blocks at high T_c yields a morphological transition from the PE lamellar morphology into a new solid morphology.