Effect of Polymer Network Morphology on the Performance of Polymer Dispersed Liquid Crystal (PDLC) Composite Films

The effects of the morphologies of liquid crystal (LC) droplets left in polymer network on the performance of polymer dispersed liquid crystal composite films were investigated.By adjusting the relative content range of the crosslinking and diluents,the morphologies of polymer network can be changed.Therefore,the properties of PDLC composite films with imparity polymer morphologies were obtained by experiments and the finite element simulation.Results of the experimental and finite element simulation showed that the electro-optical properties of PDLC composite films were inversely proportional to the domain size of the polymer network and the mechanical properties were proportional to the domain size of the polymer network.

Three-dimensional histology:new visual approaches to morphological changes during neural regeneration

Three-dimensional（3D） histology utilizes tissue clearing techniques to turn intact tissues transparent,allowing rapid interrogation of tissue architecture in three dimensions.In this article,we summarized the available tissue clearing methods and classified them according to their physicochemical principles of operation,which provided a framework for one to choose the best techniques for various research settings.Recent attempts in addressing various questions regarding the degenerating and regenerating nervous system have been promising with the use of 3D histological techniques.

Aberrant single-subject morphological brain networks in first-episode,treatment-naive adolescents with major depressive disorder

Background:Neuroimaging-based connectome studies have indicated that major depressive disorder(MDD)is associated with dis-rupted topological organization of large-scale brain networks.However,the disruptions and their clinical and cognitive relevance are not well established for morphological brain networks in adolescent MDD.Objective:To investigate the topological alterations of single-subject morphological brain networks in adolescent MDD.Methods:Twenty-five first-episode,treatment-naive adolescents with MDD and 19 healthy controls(HCs)underwent T1-weighted magnetic resonance imaging and a battery of neuropsychological tests.Single-subject morphological brain networks were constructed separately based on cortical thickness,fractal dimension,gyrification index,and sulcus depth,and topologically characterized by graph-based approaches.Between-group differences were inferred by permutation testing.For significant alterations,partial correla-tions were used to examine their associations with clinical and neuropsychological variables in the patients.Finally,a support vector machine was used to classify the patients from controls.Results:Compared with the HCs,the patients exhibited topological alterations only in cortical thickness-based networks character-ized by higher nodal centralities in parietal(left primary sensory cortex)but lower nodal centralities in temporal(left parabelt complex,right perirhinal ectorhinal cortex,right area PHT and right ventral visual complex)regions.Moreover,decreased nodal centralities of some temporal regions were correlated with cognitive dysfunction and clinical characteristics of the patients.These results were largely reproducible for binary and weighted network analyses.Finally,topological properties of the cortical thickness-based net-works were able to distinguish the MDD adolescents from HCs with 87.6%accuracy.Conclusion:Adolescent MDD is associated with disrupted topological organization of morphological brain networks,and the disrup-tions provide potential biomarkers for diagnosing and monitoring the disease.

分子间相互作用调控丝素蛋白/聚丙烯酰胺水凝胶的网络形貌和β片结晶,赋予水凝胶优异的黏附、应变和传感性能

丝素蛋白(SF)作为一种特殊的天然聚合物,具有优异的生物相容性、生物降解性和双亲性,是制备柔性传感器的良好候选者.然而,丝素蛋白的高结晶度和结晶不可控性使获得这种出色的仿生水凝胶传感器具有挑战性.纯SF水凝胶是脆性的,没有黏性.在此,我们通过引入聚丙烯酰胺(PAM)到SF水凝胶中来解决这一问题.由于SF/PAM水凝胶具有较强的分子间相互作用,其网络形貌由欧几里得孔改变为非欧几里得孔.同时,其β片结晶很容易被抑制到纳米尺度.这些演变不仅使SF/PAM水凝胶具有优异的机械性能,而且具有出色的黏附性能.与纯PAM水凝胶相比,SF8/PAM水凝胶的拉伸强度、拉伸破坏应变、抗压强度(80%应变下)和黏附性能(在猪皮上)分别提高了133.1%、120.9%、610.8%和104.8%.此外,SF的双亲性可以使碳纳米管(CNTs)在水凝胶中分散良好.制备的CNT0.3/SF8/PAM水凝胶继承并进一步改善了上述性能.除此之外,它还表现出优异的自黏附传感性能,最大灵敏度因子高达10.13,工作应变范围超过1000%,大应变下稳定循环拉伸达500次以上.同时,六种人类活动的精确检测也得到了验证.本工作为实现高性能SF基水凝胶提供了新策略,并证实SF/PAM水凝胶在柔性可穿戴应变传感器中具有广阔的应用前景.

Nanoscale 3D ordered polymer networks

Structures having nanoscale 3 D geometries are valuable as multifunctional materials, where multi-continuous microphases can synergistically influence mechanical, optical, transport and other properties. Such very high interface surface to volume ratio structures occur in a variety of materials including natural materials such as butter fly wings and sea urchin exoskeletons and in synthetic self-assembled structures such as surfactant/water systems and block polymers. Quantitative morphological characterization of such complex geometric structures is quite challenging. Unit cell sizes range from 10–300 nm with corresponding feature sizes on the 2–50 nm scale. Since these nanoscale network structures are bicontinuous, when one constituent is removed, the structure is still self supporting. Removal of one component produces a nanoporous material that may be in-filled with another component, or the surfaces of the nanopores can be coated with ultra-thin layers by atomic layer deposition to offer multifunctional capabilities. Due to the ability to individually tailor the properties of the network(s) and matrix,for example, to create strong dielectric or impedance contrast, such spatially periodic structures are excellent for the interference of waves(electromagnetic for photonic applications and acoustic for phononic applications) that can lead to bandgaps and hence the control of wave propagation in the material. This mini-review will focus on networks formed by bottom up self assembly of block polymers. In addition to structural issues, we emphasize the special physical properties related to bi-or tri-continuous networks.

Effect of polymer structures on electro-optical properties of polymer stabilized liquid crystal films

The polymer stabilized liquid crystal(PSLC)film is a relatively novel electro-optical material,which is generally obtained by dissolving a small amount of a bifunctional photoreactive monomer in a low molecular mass liquid crystal.In this paper,the PSLC films were prepared with photoreactive biphenyl methacrylate monomers by photopolymerization induced phase separation.The effects of liquid crystal concentration,curing time,monomer structures and alignment layer on the electro-optical properties of PSLC films were investigated.The results show that the transmittance in the OFF state(TOFF)increased with the liquid crystal concentration,but the driving voltage decreased.TOFF was also influenced by the curing time.Furthermore,when polyimide was used as alignment layer,the films prepared from the bifunctional monomer shows a higher TOFF,while those from the single functional monomer exhibited a deformed electro-optical curve due to the unsteady polymer networks.