Modeling the amorphous phase of comb‐like polymers

In this work, we apply a methodology recently developed by us to perform atomistic simulations of the amorphous phase of poly(α‐octadecyl β‐aspartate) and poly‐ (octadecyl acrylate). The simulation method, which is denoted SuSi/CB, combines the strength of an algorithm specially designed to generate atomistic models of dense amorphous polymers and the Configurational Bias Monte Carlo procedure. Modeling results reveal that poly(octadecyl acrylate) presents a tendency to adopt backbone helical conformations, while no trace of helicity was detected in the amorphous phase poly(α‐octadecyl β‐aspartate). Regarding the side chain organization, the paraffinic pool formed by the octadecyl side chains is slightly greater for the poly(acrylate) than for the poly(β‐aspartate). According to these features, it can be concluded that the small chemical differences between the two investigated polymers are enough to provide some distinctive structural features. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 953–966, 2006     

Performance of SuSi: a method for generating atomistic models of amorphous polymers based on a random search of energy minima

The performance of a recently developed method to generate representative atomistic models of amorphous polymers has been investigated. This method, which is denoted SuSi, can be defined as a random generator of energy minima. The effects produced by different parameters used to define the size of the system and the characteristics of the generation algorithm have been examined. Calculations have been performed on poly(L,D-lactic) acid (rho = 1.25 g/cm3) and nylon 6 (rho = 1.084 g/cm(3)), which are important commercial polymers.     

Simulation of Amorphous Nylon 6 Using SuSi,a Strategy Based on Generation–Relaxation Algorithms

Summary: The ability of SuSi to generate microstructures of polymers with hydrogen bonding interactions has been checked. This is a random procedure recently developed to localize independent minima. Calculations were performed on nylon 6, a large number of equilibrated and relaxed atomistic models, i.e. microstructures without torsional strain and atomic overlaps, being generated. Results indicated that the generation algorithm implemented in SuSi underestimates the amount of amide groups involved in hydrogen bonding interactions. This is an expected result since no specific criterion was introduced in it to facilitate the formation of specific interactions. Several modifications have been introduced in the generation algorithm to overcome this limitation. The changes induced by these modifications in the generated microstructures are discussed.

A new computational strategy denoted SuSi generates atomistic models of hydrogen bond forming polymers with very reliable results.     

Influence of γ-ray Irradiation on the PTC Effect of EPDM/Carbon Black Composite

Introduction The positive temperature coefficient(PTC) effect is characterized by an increase of resistivity with an elevated temperature.The PTC effect of carbon black(CB) filled polymers is useful for self-regulation heaters,over-current protectors,sensors,etc.Much work has been done on the PTC effect of the carbon black filled crystalline polymer composite[1-4],whereas carbon black filled amorphous polymers have not drawn researchers much attention because the PTC effect in these composites is small or cannot be detected[5-7].In this work,the influence of γ-ray irradiation on the PTC effect of CB filled amorphous ethylene-propylene-diene terpolymer(EPDM) composites was studied.     

Supramolecular self-assembling strategy for constructing cucurbit[6]uril derivative-based amorphous pure organic room-temperature phosphorescence complex featuring extra-high efficiency

The preparation of amorphous pure organic room-temperature phosphorescence materials with high efficiency is still a challenging task. Herein, we introduce a CB[6] derivative-based supramolecular self-assembling strategy. A water soluble and ellipsoidal deformed CB[6] derivative is used to self-assemble with 4-(4-bromophenyl)-1-methylpyridin-1-ium chloride, bromide and hexafluorophosphate in water. After freeze-drying, the obtained amorphous complexes exhibit brilliant green phosphorescence emission under ambient conditions, with phosphorescence efficiency up to 59%, 60% and 72%, respectively. This is the first report of amorphous non-polymeric pure organic room-temperature phosphorescence with such a high efficiency. In view of the dynamic self-assembling property, the complexes are responsive to water, which could enable information encryption.     

INVESTIGATION OF MICROSTRUCTURE AND CONDUCTIVE MECHANISM OF HIGH DENSITY POLYETHYLENE/CARBON BLACK PARTICLE COMPOSITE BY POSITRON ANNIHILATION LIFETIME SPECTROSCOPY

The microstructure and conductive mechanism of high density polyethylene/carbon black (HDPE/CB) compositewere investigated by positron annihilation lifetime spectroscopy (PALS). The PALS were measured in two series of samples,one with various CB contents in the composites and the other with various γ-irradiation doses in HDPE/CB compositecontaining 20 wt% CB. It was found that CB particles distribute in the amorphous regions, the CB critical content value inHDPE/CB composite is about 16.7 wtO/ and the suitable γ-irradiation dose for improving the conductive behavior ofHDPE/CB composite is about 20 Mrad. T'he result observed for the second set of samples suggests that γ-irradiation causesnot only cross-linking in amorphous regions but also destruction of the partial crystalline structure. Therefore, a suitableirradiation dose, about 20 Mrad, can induce sufficient cross-linking in the amorphous regions without enhancing thedecomposition of crystalline structure, so that the positive temperature coefficient (PTC) effect remains while the negativetemperature coefficient (NTC) effect is suppressed. A new interpretation of the conductive mechanism, which might providea more detailed explanation of the PTC effect and the NTC effect has been proposed.     

Engineering living cells with cucurbit[7]uril-based supramolecular polymer chemistry: from cell surface engineering to manipulation of subcellular organelles

Supramolecular polymer chemistry, which closely integrates noncovalent interactions with polymeric structures, is a promising toolbox for living cell engineering. Here, we report our recent progress in exploring the applications of cucurbit[7]uril (CB[7])-based supramolecular polymer chemistry for engineering living cells. First, a modular polymer-analogous approach was established to prepare multifunctional polymers that contain CB[7]-based supramolecular recognition motifs. The supramolecular polymeric systems were successfully applied to cell surface engineering and subcellular organelle manipulation. By anchoring polymers on the cell membranes, cell–cell interactions were established by CB[7]-based host–guest recognition, which further facilitated heterogeneous cell fusion. In addition to cell surface engineering, placing the multifunctional polymers on specific subcellular organelles, including the mitochondria and endoplasmic reticulum, has led to enhanced physical contact between subcellular organelles. It is highly anticipated that the CB[7]-based supramolecular polymer chemistry will provide a new strategy for living cell engineering to advance the development of cell-based therapeutic materials.

Cucurbit[7]uril-based supramolecular polymer chemistry, which closely integrates host–guest recognition with multifunctional polymeric structures, is a promising toolbox for living cell engineering.     

Mechanical and rheological properties of poly(ethylene-co-ethyl acrylate) as a function of carbon black content

Carbon black (CB) filled poly(ethylene-co-ethyl acrylate) (EEA-CB) is used as conductive phase in conductive polymer composites (CPC). Electrical conductivity of CPC obtained from blends of immiscible polymers results from CB particles localization within the material, which depends on composition and processing conditions. It is particularly important to control viscosity of such systems as this parameter determines both the phase morphology and conductive pathway structure. The small scale, at which CB particle aggregation/dispersion phenomena occur within CPC, makes direct observations difficult. But the effect of carbon black particles/polymers interactions is clearly visible by means of rheological measurements. A strong reinforcing effect of CB on CPC in both solid and liquid states has been noticed. This phenomenon has been analyzed using classical models as a function of temperature and CB content. The results confirm the necessity of CPC rheology control especially during the process to achieve good reproducibility of electrical properties.     

A Synergistic Enhancement Strategy for Realizing Ultralong and Efficient Room-Temperature Phosphorescence

An enhancement strategy is realized for ultralong bright room-temperature phosphorescence (RTP), involving polymerization between phosphor monomers and acrylamide and host–guest complexation interaction between phosphors and cucurbit[6,7,8]urils (CB[6,7,8]). The non-phosphorescent monomers exhibit 2.46 s ultralong lifetime after copolymerizing with acrylamide. The improvement is due to the rich hydrogen bond and carbonyl within the polymers which promote intersystem crossing, suppress nonradiative relaxation and shield quenchers effectively. By tuning the ratio of chromophores, a series of phosphorescent copolymers with different lifetimes and quantum yields are prepared. The complexation of macrocyclic hosts CB[6,7,8] promote the RTP of polymers by blocking aggregation-caused quenching, and offsetting the losses of aforementioned interaction provided by polymer. Multiple lifetime-encoding for digit and character encryption are achieved by utilizing the difference of their lifetimes.     

结晶高分子非晶区的结构及其动力学行为研究进展

非晶结构对结晶高分子材料结构和最终使用性能有非常重要的影响,但目前对半晶高分子中非晶结构的认识还不太清晰并且有待进一步完善.随着研究手段的发展,结晶高分子中非晶区结构及其动力学行为的研究受到越来越多的关注.本文简要概述了目前对结晶高分子中非晶相的研究进展,主要从结晶高分子中非晶区的结构﹑结晶高分子中非晶区的松弛行为﹑非晶相对结晶高分子性能的影响以及等温结晶过程中非晶相的结构演化这四个方面进行介绍,并对它们的研究现状进行了概述,同时指出了目前在这方面研究中存在的争议和问题.     

Influence of the presence of small gas molecules in the structure of comblike polyacrylates: a Monte Carlo study

A theoretical strategy has been developed to study the motion of small molecules through ordered polymeric systems. The strategy, which has been incorporated into a computer program denoted MCDP/2, is especially useful to study comblike polymers organized in biphasic arrangements. This is because it is based on a configurational bias Monte Carlo algorithm, which is more efficient than conventional methods to study dense systems. The MCDP/2 program has been used to investigate the influence of CH(4) and CO(2) gas molecules in the structure of isotactic poly(octadecyl acrylate), a typical comblike polymer. For this purpose, the pure polymer and different molecular systems constituted by several gas molecules dissolved in the polymer matrix have been simulated. Results indicated that the structural relaxation of the polymer is not coupled to the motion of gas molecules. The importance of these results in the field of molecular modeling of transport properties in comblike polymers is discussed.     

Thermally Tunable Hydrogels Displaying Angle‐Independent Structural Colors

We report the preparation of thermally tunable hydrogels displaying angle‐independent structural colors. The porous structures were formed with short‐range order using colloidal amorphous array templates and a small amount of carbon black (CB). The resultant porous hydrogels prepared using colloidal amorphous arrays without CB appeared white, whereas the hydrogels with CB revealed bright structural colors. The brightly colored hydrogels rapidly changed hues in a reversible manner, and the hues varied widely depending on the water temperature. Moreover, the structural colors were angle‐independent under diffusive lighting because of the isotropic nanostructure generated from the colloidal amorphous arrays.     

GPCR structure-based virtual screening approach for CB2 antagonist search

The potential for therapeutic specificity in regulating diseases has made cannabinoid (CB) receptors one of the most important G-protein-coupled receptor (GPCR) targets in search for new drugs. Considering the lack of related 3D experimental structures, we have established a structure-based virtual screening protocol to search for CB2 bioactive antagonists based on the 3D CB2 homology structure model. However, the existing homology-predicted 3D models often deviate from the native structure and therefore may incorrectly bias the in silico design. To overcome this problem, we have developed a 3D testing database query algorithm to examine the constructed 3D CB2 receptor structure model as well as the predicted binding pocket. In the present study, an antagonist-bound CB2 receptor complex model was initially generated using flexible docking simulation and then further optimized by molecular dynamic and mechanical (MD/MM) calculations. The refined 3D structural model of the CB2-ligand complex was then inspected by exploring the interactions between the receptor and ligands in order to predict the potential CB2 binding pocket for its antagonist. The ligand-receptor complex model and the predicted antagonist binding pockets were further processed and validated by FlexX-Pharm docking against a testing compound database that contains known antagonists. Furthermore, a consensus scoring (CScore) function algorithm was established to rank the binding interaction modes of a ligand on the CB2 receptor. Our results indicated that the known antagonists seeded in the testing database can be distinguished from a significant amount of randomly chosen molecules. Our studies demonstrated that the established GPCR structure-based virtual screening approach provided a new strategy with a high potential for in silico identifying novel CB2 antagonist leads based on the homology-generated 3D CB2 structure model.     

Pyrrole/macrocycle/MOF supramolecular co-assembly for flexible solid state supercapacitors

Supramolecular assemblies constructed through the encapsulation of conductive polymers (CPs) by macrocyclic molecules have attracted increasing interest in the fields of supramolecular chemistry and electrochemistry. In this work, an effective strategy was reported to improve the stability and conductivity of CPs by electrochemically constructing different supramolecular assemblies composed of macrocycles and CPs. Typically, we uploaded zinc-based MOF (ZIF-8) onto carbon nanotube film (CNTF) and further electrically deposited macrocycles and CPs to gain the flexible conductive electrodes. Herein, five different supramolecular macrocycles, including α-cyclodextrin (α-CD), sulfato-β-cyclodextrin (SCD), sulfonatocalix[4]arene (SC[4]), cucurbit[6]uril (CB[6]) and cucurbit[7]uril (CB[7]) were utilized and the electrochemical performances of the assembly electrodes increased in an order of α-CD < SCD < SC[4] < CB[6] < CB[7], significantly improving the areal capacitance up to 1533 mF/cm². This strategy may provide a new way for the application of macrocyclic supramolecules in electrochemical systems.     

Thermal conductivity behaviour of polymers around glass transition and crystalline melting temperatures

The thermal conductivity of five semi-crystalline and four amorphous polymers was determined within a wide range of temperature, starting at room temperature and going up to temperatures above the polymer melting point (Tm) for semi-crystalline polymers or above the glass transition temperature (Tg) for amorphous polymers. Two transient techniques were employed in the experimental investigation: the hot wire technique for the group of amorphous polymers, and the laser flash technique for the semicrystalline polymers. As expected, the experimental results show that Tg exerts a measureable influence on the thermal conductivity of amorphous polymers. In the case of semi-crystalline polymers, a singular behaviour of the thermal conductivity is observed within the Tm range. In order to explain the anomalous behaviour, the influence of these transition temperatures on the thermal conductivity behaviour with temperature has been analysed in terms of a phonon conduction process and temperature variations of specific heat and modulus of elasticity of the analyzed polymers.     

Relationship between electrical resistivity and particle dispersion state for carbon black filled poly (ethylene-<Emphasis Type="Italic">co</Emphasis>-vinyl acetate)/poly (<Emphasis Type="SmallCaps">L</Emphasis>-lactic acid) blend

It is known that the electrical volume resistivity of insulating polymers filled with conductive fillers suddenly decreases at a certain content of filler. This phenomenon is called percolation. Therefore, it is known that controlling resistivity in the semi-conductive region for carbon black (CB) filled composites is very difficult. When poly (ethylene-co-vinyl acetate) (EVA) is used as a matrix, the percolation curve becomes gradual because CB particles disperse well in EVA. In this study, the relationship between the dispersion state of CB particles and electrical resistivity for EVA/poly (L-lactic acid) (PLLA) filled with CB composite was investigated. The apparent phase separation was seen in the SEM photograph. It was predicted that the CB particles located into the EVA phase in the light of thermodynamical consideration, which was estimated from the wetting coefficient between polymer matrix and CB particles. The total surface area per unit mass of dispersed CB particles in the polymer blend matrix was estimated from small-angle X-ray scattering and the volume resistivity decreased with increasing CB content. The values of the surface area of CB particles in CB filled EVA/PLLA (25/75 wt%) and EVA/PLLA (50/50 wt%) polymer blends showed a value similar to that of the CB filled EVA single polymer matrix. In electrical volume resistivity measurement, moreover, the slopes of percolation curves of EVA/PLLA (25/75 wt%) and EVA/PLLA (50/50 wt%) filled with CB composite are similar to that of EVA single polymer filled with CB composite. As a result, it was found that CB particles selectively locate in the EVA phase, and then the particle forms conductive networks similar to the networks in the case of EVA single polymer used as a matrix.     

利用原位微纤化技术控制聚合物形态的研究进展

综述了利用原位微纤化技术控制聚合物形态的研究进展,简要介绍了原位微纤化共混物的概念、制备方法、影响成纤的因素及常见原位微纤化体系等,讨论了原位微纤化技术对碳纳米管(CNTs)/聚碳酸酯(PC)/聚乙烯(PE)、碳黑(CB)/对苯二甲酸乙二醇酯(PET)/PE及纳米碳酸钙(nano-CaCO3)/CB/PET/PE等体系的形态调控以及体系形态与力学性能、电学性能的关系,简要介绍了原位微纤化技术在废旧塑料回收方面的应用,最后阐述了原位微纤化技术的重要性并展望了其应用前景.     

Piezoelectric polymer films. II. Piezoelectric and pyroelectric evaluation

The concept of piezoelectric and pyroelectric effects in amorphous polymers is presented, with experimental results, details on sample preparation, and activity evaluation. Most evaluations were performed on 25–30 mol% tributyltin methacrylate/methyl methacrylate copolymers, which possessed good piezoelectric activity, antifouling properties, and paint-formulation characteristics. Solvent-induced orientation effects that lead to piezoelectric activity in amorphous, unpoled, polymers are also described.     

瓜环基金属纳米催化剂的电化学研究进展（英文）

金属纳米材料在电催化应用中展示出良好的性能,但是它们依旧面临着稳定性差和调控策略有限的问题。引入第二组分是一种有效的策略,能够很好的改善其催化活性与稳定性。在这篇综述中,我们概述了结合金属纳米材料和瓜环（CB[n]）用于电催化应用。瓜环是一系列的具有刚性结构、高稳定性、与金属配位的官能团的大环,它们适合稳定金属纳米材料并对其进行调控。本文讨论按照瓜环的功能分类,包含瓜环作为保护剂、瓜环基的超分子自组装体以及瓜环作为前驱体制备氮掺杂多孔碳。多种金属纳米催化剂,包括金属纳米颗粒（Pt,Ir,Pd,Ru,Au）、金属单原子（Fe,Co,Ni）以及过渡金属碳化物（TMCs）成功与瓜环或瓜环衍生的碳材料复合,这些复合材料在许多电催化反应中展示出优异的性能和稳定性,反应包括了氧还原反应（ORR）、析氧反应（OER）、析氢反应（HER）、二氧化碳还原反应（CO2RR）、甲烷氧化反应（MOR）、乙醇氧化反应（EOR）。其中,一些金属-瓜环复合物可进一步作为双功能催化剂用于全水解和燃料电池中。瓜环基的纳米催化剂具有媲美商用催化剂的性能,甚至其稳定性可优于商用催化剂。实验分析以及密度泛函理论（DFT）计算...     

流变-导电同步测试法研究炭黑填充高密度聚乙烯的等温结晶行为

采用流变-导电同步测试法,研究炭黑(CB)填充高密度聚乙烯(HDPE)在124.3～125.3℃范围的等温结晶行为,发现应变、频率与预降温速率均显著影响等温结晶过程中动态流变与导电行为.动态储能模量(G')与电阻均在结晶过程中发生显著变化.其中,CB粒子在熔体中发生扩散,造成原有逾渗网络结构破坏,导致复合体系电阻在结晶诱导期内增大.随结晶度增加,G'在结晶诱导期附近开始显著增大,其临界时间对应1%～2%相对结晶度;同时,CB粒子在无定形区相互聚集而形成渗流网络结构,使得复合体系电阻显著降低.电阻的变化被认为与CB粒子在熔体中的迁移以及在HDPE晶体生长过程中的聚集行为有关,且比依时性动态流变行为更敏感.