湖相细粒沉积岩纹层结构差异对可压裂性的影响

细粒沉积岩纹层结构（如纹层发育程度、厚度大小、厚度差异性和连续度）是影响岩石力学性质以及裂缝扩展的内在因素。通过对中国东部中生代-新生代的湖相细粒沉积岩开展研究，以常规三轴实验和断裂韧性实验为基础，结合图像分析和处理技术，分析了不同纹层结构与岩石力学参数之间的对应关系，综合评价了湖相细粒沉积岩纹层结构差异对可压裂性的影响。研究表明，细粒沉积岩的可压裂性指数与纹层数量、连续度呈负相关，但与纹层厚度方差、颗粒垂向分布方差呈正相关。纹层发育且连续性强的细粒沉积岩，其塑性较强，压裂缝以沿纹层界面或塑性纹层（黏土纹层或有机质纹层）扩展为主，裂缝易再次闭合，从而导致岩石的可压裂性降低。纹层厚度差异性较大、颗粒垂向分布均匀度较高的细粒沉积岩，其脆性较高，在压裂过程中易形成复杂有效的网状缝，从而提高岩石的可压裂性。此外，细粒沉积岩组分、颗粒结构以及成岩作用对可压裂性也具有重要的控制作用。     

Structural analysis of oriented poly(ε‐caprolactone) including CaCO3 particles with 13C solid‐state NMR

The results of a study of the relation between the oriented structure and drawn Poly(ε‐caprolactone) specimens including CaCO₃ particles and their dynamic mechanical properties are presented. The loss elasticity, E″, showed almost the same curve for both undrawn sheets and drawn sheets as a function of CaCO₃ content. On the other hand, the storage modulus, E′, of drawn sheets increased nonlinearly with increasing CaCO₃ content, and their curve showed lower E′ values than those of undrawn sheets. By simulation of ¹³C CP NMR spectra of drawn PCL/CaCO₃ sheets, both oriented and unoriented components were observed. The distribution parameter, p, of drawn PCL/CaCO₃ sheets was 13°, which was larger than those (8°) of drawn PCL. Further, the fraction of the unoriented component increased with increasing CaCO₃ content. Thus, adding CaCO₃ particles into the PCL, the arrangement of the oriented component was disturbed and decreased. In addition, from the line shape analyses of ¹³C CP MAS NMR spectra, four peaks were obtained in not only undrawn sheets but also in drawn sheets of both PCL and PCL/CaCO₃ compounds. Besides, structural change occurred at only drawn PCL/CaCO₃ sheets. Therefore, the change in dynamic mechanical properties observed only for drawn PCL/CaCO₃ sheets were strongly dependent on the orientational structure, which was formed under shear stress of the stretching drawn process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2376–2382, 2001     

Study on a series of main-chain liquid–crystalline ionomers containing sulfonate groups

A series of main-chain liquid–crystalline ionomers containing sulfonate groups pendant on the polymer backbone were synthesized by an interfacial condensation reaction of 4,4′-dihydroxy-α,α′-dimethyl benzalazine, a mesogenic monomer, with brilliant yellow (BY), a sulfonate-containing monomer, and a 1/9 mixture of terephthaloyl and sebacoyl dichloride. The structures of the polymers were characterized by IR and UV spectroscopies. DSC and thermogravimetric analysis were used to measure the thermal properties of those polymers, and the mesogenic properties were characterized by a polarized optical microscope, DSC, and wide-angle X-ray diffraction. The ionomers were thermally stable to about 310 °C. They were thermotropic liquid–crystalline polymers (LCPs) with high mesomorphic-phase transition temperatures and exhibited broad nematic mesogenic regions of 160–170 °C, and they were lyotropic LCPs with willowy leaf-shaped textures in sulfuric acid. However, the thermotropic liquid–crystalline properties were somewhat weakened because the concentration of BY was more than 8%. The inherent viscosity in N-methyl-2-pyrrolidone suggested that intramolecular associations of sulfonate groups occurred at low concentration, and intermolecular associations predominated at higher concentration. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2210–2218, 2001     

Freezing the orientation of a nematic stretched elastomer by photocrosslinking

In this paper we tried to prepare shape memory main chain LC materials, by photopolymerizing (UV-curing) LC elastomers subjected to uniaxial stress. For this purpose, we prepared blends, having different compositions, of a well-known mesogenic diglycidyl-terminated monomer, namely 4,4′-diglycidyloxybiphenyl (DIF), with its homologous bearing lateral photocurable allyl groups (AllDIF). The obtained blends were thermally cured with an aliphatic diacid (decandioic acid, SA), and gave LC networks in all the cases but 100% AllDIF composition. LC networks corresponding to a selected blend composition were subsequently conditioned with a radical photoinitiator, namely 2-hydroxy-2-methyl-1-phenyl propan-1-one and photocrosslinked by UV-curing either as such or while subjected to uniaxial stress. The characteristics of the resulting networks were investigated by means of DSC, XRD, POM, FT-IR, DMTA, and TMA analyses. The effect of UV-curing under stretching and of photoinitiator uptake on the LC phase stability and on the orientation of the networks, as well as on their dynamic-mechanical and thermomechanical response are discussed.     

The effect of chain packing on the thermal and dynamic mechanical behaviour of liquid‐crystalline epoxy thermosets

Liquid‐crystalline thermosets (LCTs) have received considerable attention since they exhibit many interesting properties. However, some aspects concerning LCTs are still unexplored. In particular, the structure–property relationships, as far as the organization of liquid‐crystalline (LC) domains in cured thermosets is concerned, have not been fully elucidated yet. We investigated the effect of the presence of a nematic mesophase on the thermal and dynamic mechanical behaviour of p‐(2,3‐epoxypropoxy)phenyl‐p‐(2,3‐epoxypropoxy)benzoate cured with 2,4‐diaminotoluene. Fourier transform infrared spectral analysis showed that epoxy group conversion was complete in both LC and isotropic (ISO) systems; moreover, a greater amount of intermolecular hydrogen bonding in the LC material was found. Thermogravimetric analysis evidenced similar thermal stability for the two systems, but a kinetic analysis of the data showed that the degradation process is more complex for the LC sample, and is characterized by higher activation energy. Dynamic mechanical thermal analysis (DMTA) showed lower glass transition temperature values for the LC system. Solid‐state NMR analysis evidenced lower paramagnetic oxygen absorption for this system. DMTA results show that the ISO material possesses a larger number of physical crosslinks, which act as extra constraints on the molecular motions. In the case of the LCT, the formation of a locally more dense structure is postulated, where the presence of more extended macromolecular segments leads to a smaller number of physical crosslinks, as also confirmed by solid‐state NMR analysis. A more compact molecular packing also leads to an increase of the activation energies of the thermal degradation process of the LC system. Copyright © 2010 Society of Chemical Industry     

Evolution of aggregation structure of polyacrylonitrile fibers in the cyclization reaction

The aggregation structure of polyacrylonitrile precursor evolves gradually with progress of cyclization. In this work, the variety of cyclization degrees were determined by Fourier transform infrared spectroscopy and the evolution of aggregation structure of PAN fibers were characterized by wide‐angle X‐ray diffraction. Experimental results showed that the cyclization occurred first in the amorphous parts when the heating temperature was below 200°C. After heated at 200°C for 30 min, molecular chains in the pseudo‐crystalline regions started to pack into crystalline regions due to the increasing stress which was produced by cyclization occurred in the amorphous phase, and the crystallinity and crystallite size increased slowly. When the temperature reached to 220°C, pseudo‐crystalline regions rearranged obviously under stress, while molecular chains in the crystalline region started to participate in cyclization, and the original crystalline structures were destructed. The two competitive processes induced that the crystallinity and crystallite size grew to the maximum values at 30 min. When the temperature up to 240°C, the cyclization occurred in the crystalline region became more intensely, while the crystallinity and crystallite size decreased out of synchronize. A scheme of evolution of aggregation structure in cyclization was modified based on the above results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Investigation on thermotropic liquid crystalline and photocrosslinkable polyarylidene arylphosphate esters containing cyclohexanone units

Two series of novel liquid crystalline-cum-photocrosslinkable divanillylidene cyclohexanone containing polymers have been synthesized from 2,6-bis[m-hydroxyalkyloxy(vanillylidene)]cyclohexanone [m=6, 8, 10] with different arylphosphorodichloridates (naphthyl, biphenyl) by solution polycondensation method at ambient temperature. Their chemical structures were confirmed by FT-IR, ¹H, ¹³C and ³¹P NMR spectroscopy. The intrinsic viscosity values were measured to find out molecular weight of the synthesized polymers. The mesogenic properties and phase behaviors were investigated with differential scanning calorimetry and hot stage optical polarized microscopy. The experimental results demonstrated that the mesogenic transition and isotropization temperature gradually decreases with increase in even number of methylene spacer of the polymer chain. All the polymers showed anisotropic behavior under hot stage optical polarized microscope (HOPM). The thermal behaviors of the polymers were studied by thermogravimetric analysis and stable between 292 and 330 °C. The photocrosslinking of the polymers was investigated in thin film by UV light/UV spectroscopy and the cyclobutane ring formation via 2π-2π cycloaddition reactions of the divanillylidene exo-cyclic double bond of the polymer backbone. The pendant naphthyloxy containing polymers show faster crosslinking than the pendant biphenyloxy containing polymers.     

带双甲基丙烯酰基偶氮苯液晶化合物的合成与表征

合成了一毓新的带双甲基丙烯酰基偶氮苯液晶化合物，并利用元素分析、红外光谱、核磁共振谱及热台偏光显微镜等方法对其进行了不征。     

Continuous and Discrete Dynamics of Heterogeneous Mesogenic Polymer Chain

Abstract

Two types of dynamic models–continuous and lattice–are considered describing a heterogeneous liquid-crystalline polymer chain built from mesogenes and spacers. The chain heterogeneity leads to enriching a set of possible motions of the chain. Each branch of the chain relaxation spectrum consisting of the isotropic phase of one acoustic and some optical branches is shown to be split into a longitudinal and transverse components. The magnitude of the splitting is found to depend on the scale of motions and the mechanism of the chain mobility. The dependence of the relaxation times on the degree of order is shown to be different for the chains with rigid and flexible spacers.     

Self-assembled liquid crystalline nanoparticles as an ophthalmic drug delivery system. Part I: influence of process parameters on their preparation studied by experimental design

To develop self-assembled liquid crystalline nanoparticles as a drug delivery system for keratoconus treatment, a formulation containing riboflavin a water-soluble drug, two surfactants (poloxamer 407 and mono acyl glycerol – monoolein-) and water was optimized and prepared by emulsification and a homogenization process. A fractional factorial design was applied to estimate the main effects and interaction effects of five parameters on two responses, namely particle size and encapsulation efficiency. The five parameters are the temperature of the two phases, the duration of emulsification, the presence of heating during homogenization, the number of passes and pressure. The most influent parameters are the presence of heating during the homogenization and the pressure that led to the production of nanoparticles with an average size of 145?nm and an average encapsulation efficiency of 46%.