LIQUID CRYSTAL POLYMERS WITH TWO-DIMENSIONAL MESOGENIC UNITS

A series of 'liquid crystal polymers with two-dimensional mesogeuic units' were synthesized by the polycondensations of the monomer 2, 5-dihydroxybenzylidene-4-phenetidine with a diacid chloride selected from a series of α, ω-bis(4-chloroformylphenyloxy)carbonylalkues. This is the first series of polymers reported under the newly proposed concept 'liquid crystal polymers with two dimensional mesogenic units'.

Syntheses of Cellulose-Type Polysaccharide by Means of Ring-Opening Copolymerization of Anhydroriboses ABRP and AIRP

Two kinds of 1,4-anhydroribose derivatives,1,4-anhydro-2,3-O-benzylidene-T-D-ribopyranose(ABRP)and 1,4-anhydro-2,3-O-isopropylidene-T-D-ribopyranose(AIRP)were prepared fromD-ribose.The ringopening copolymerizations of ABRP and AIRP in various feed ratios were carried out with SbCl_5 and BF_3OEt_2 as catalyst at low temperatures.The copolymer structure was characterized by means of ^(1)H,^(13)C NMR spectroscopy and specific rotation.When SbCl_(5)was used as catalyst,the copolymer obtained had completely 1,4-β-pyranosidic structure,i.e.,cellulosetype structure.However,when BF_(3)OEt_2 was used as catalyst,the copolymer had a mixed structure of furanosidic and pyranosidic units.

SYNTHESIS AND PROPERTIES OF NEW SIDE-CHAIN LIQUID CRYSTALLINE POLYMER WITH LATERALLY ATTACHED MESOGENS BY ESTER GROUP

New liquid crystalline monomer,2,5-bis[(4'-methoxyphenoxy)carbonyl]phenyl acrylate was successfully synthesized.Polyacrylate with laterally attached mesogens via ei;ter linkage was also derived.This polymer forms an enantiotropic liquid crystal phase while its monomer exhibits a metastable nematic phase with respect to the crystalline state.However,its liquid crystallinity is very low as compared to that of poly{2,5-bis[(4'-methoxyphenoxy)carbonyl]-styrene}.

31P核磁共振波谱表征高聚合度聚磷酸铵及其链结构

以液体定量^(31)P核磁共振波谱(^(31)P NMR)为主要表征手段,通过建立水中加盐促溶的高聚合度聚磷酸铵(APP)水溶液的制备方法,研究不同溶解温度、测试温度及NMR参数等对APP聚合度的影响,建立了^(31)P NMR准确表征APP的聚合度及其链结构的方法.研究结果表明,于36℃在水中加盐溶解APP,26℃下进行^(31)P NMR测试,既保证了APP溶液良好的溶解性,又在水溶液制备和^(31)P NMR测试过程中不引起APP降解,测得的APP聚合度稳定、准确.利用液体^(31)P NMR确定了不同温度下APP盐水溶液中端基磷和中间磷弛豫时间(T_1),发现T_1与温度呈线性关系,弛豫时间参数(D_1)的设置影响APP聚合度结果,D_1设置不满足磷所需的T_1时,APP的聚合度结果偏大.^(31)P NMR表征APP链结构结果显示,APP的端基磷存在3种化学环境,而溶液离子强度和温度会影响3种端基磷的化学位移;APP的中间磷中含有H^+.此外,提出了中国化工行业标准HG/T 2770-2008中APP高聚合度测定存在的问题.

The potential of pervaporation for biofuel recovery from fermentation:An energy consumption point of view

Recovering alcohols from dilute fermentation broth is an emergent task in bio-fuel production process. Since they are primary planned for fuels, energy required to separate these alcohols should be considered in evaluating the potential of a separation technology. A membrane-based process, pervaporation, is of special interest because of its environmental friendliness and easy integrating character. This review probes into the fundamentals of pervaporation especially in terms of the heat required for evaporation. Meanwhile, the separation data of the most representative alcohol-selective pervaporation membranes reported in the literatures are collected and compared with the vapor–liquid equilibrium curve, which represents the distillation selectivity. They include:inorganic membranes, silicon rubber based membranes, Mixed Matrix Membranes and some other special materials. By doing so, the status of alcohol recovery via pervaporation would be more clear for researchers.For ethanol recovery, it is selectivity rather than flux that is in urgent need of solution. While for butanol recovery,membranes with satisfactory selectivity have been developed, increasing the separation capacity would be more pressing.

A More Efficient Synthetic Route to Perylene-porphyrin Arrays

We present an efficient synthetic route towards two kinds of perylene-porphyrin arrays. Starting from 5, 10, 15, 20-meso-tetraphenylporphyrin, two novel 9a and 9b were designed and synthesized with 40.3% and 35.1% yield, respectively.

高聚合度聚磷酸铵中特征磷的31P核磁共振分析

采用一维31P核磁共振(31P NMR)、二维J分解谱(J-resolved)和扩散核磁(31P DOSY)等方法,研究了高聚合度聚磷酸铵(APP)和多聚磷酸盐的特征磷及其偶合常数.研究表明,多聚磷酸盐及其中所含的二聚磷酸盐端基磷分别呈双峰和单峰特征,多聚磷酸盐自旋偶合裂分的端基磷共振峰的偶合常数为19.4 Hz.APP中含有小分子二聚磷酸铵和正磷酸铵,用31P NMR定量表征APP聚合度时需排除二聚体端基磷峰的面积.在100℃水中溶解APP制备的APP水溶液中,部分高聚合度APP发生断链,中间磷共振峰处出现短链APP的磷共振峰.

Reduction of Aromatic Aldehydes and Ketones with Acyloxy Substituent at the Ortho-position by NaBH_4 in the Presence of Waters

An unusual reduction of some aromatic aldehydes and ketones by sodium borohydride was discovered.In a THF/H2O or DMSO/H2O solvent system the aromatic aldehydes and ketones with acyloxy substituent on the orthoposition to the carbonyl group can be reduced to the corresponding alkyl phenols.This unusual reduction is applicable also to the corresponding alcohols of all the above aldehydes and ketones.A putative mechanism was suggested.In addition to the above aldehydes,ketones and benzyl alcohols,certain 4acyloxybenzyl esters(probably also the 2substituted analogues)such as 4benzoyloxybenzyl benzoate was also found to be reduced to methylphenol by this unusual reduction.

Effect of poly(4-tert-butylstyrene)block length on the microphase structure of poly(ethylene oxide)-b-poly(4-vinylbenzyl chloride)-b-poly(4-tert-butylstyrene)triblock terpolymers

A series of linear poly(ethylene oxide)-b-poly(4-vinylbenzyl chloride)-b-poly(4-tert-butylstyrene)(PEO_(113)-b-PVBC_(130)-b-Pt BS_(x)or E_(113)V_(130)T_(x))triblock terpolymers with various lengths x(=20,33,66,104,215)of Pt BS block were synthesized via a two-step reversible addition-fragmentation chain transfer(RAFT)polymerization.The E_(113)V_(130)T_(x)triblock terpolymers were non-crystalline because the PVBC and Pt BS blocks strongly hindered the crystallization of PEO block.The effects of Pt BS block length x on the phase structures of E_(113)V_(130)T_(x)triblock terpolymers were investigated by combined techniques of small-angle X-ray scattering(SAXS)and transmission electron microscopy(TEM).It was found that with increasing x from20 to 215,the phase structure of E_(113)V_(130)T_(x)triblock terpolymers became more ordered and changed from disordered structure,hexagonally-packed cylinder(HEX),hexagonally perforated layer(HPL),to lamellar(LAM)phase structures.Temperature-variable SAXS measurements showed that the HEX,HPL and LAM phase structures obtained for E_(113)V_(130)T_(66),E_(113)V_(130)T_(104)and E_(113)V_(130)T_(215)by thermal annealing,respectively,were thermodynamically stable in the temperature range of 30-170℃.

Construction of Aniline Trimer Based Conjugated Polymers through Schiff Base Reaction and Their Use as Feedstock for Infrared Stealth Coatings

In order to meet the demand for infrared stealth materials in the military field,conjugated polymers containing Schiff base moieties were designed and prepared.Various dialdehyde monomers were introduced and their effect on the comprehensive properties were systematically characterized.The resulted polymers could be cast in solution to prepare polymer coatings.The coatings exhibited high thermal stability up to 400℃ at 5%weight loss,and excellent mechanical performance with high Young’s modulus and hardness.The infrared emissivity values varied from 0.587 to 0.627 at wavelength of 8-14μm and ranged from 0.595 to 0.609 at wavelength of 2-22μm.Specifically,it was found that the ATTPAL structure with carbazole moieties had a lower band gap and better electrical conductivity by photoelectric test and DFT theoretical analysis.Meanwhile,the infrared emissivity value of ATTPAL coating was the lowest compared with p-phenyl and pyridyl containing analogues,suggesting it was potential material for the future development of infrared stealth technology.The combined results showed that reducing the band gap and improving the electrical conductivity of the structure were both beneficial to the reduction of infrared emissivity.It would positively provide new ideas for the design of infrared stealth materials.

Electromagnetic wave absorption performance and rheological behavior of rubber composites with low mass filling rate carbon nanofiber aerogel

With the development of electronic information science and technology,electromagnetic information security and electromagnetic pollution become more and more serious.Electromagnetic wave absorption(EMWA)rubber based on the absorbent of carbon with low density and good corrosion resistance is a kind of good EMWA materials for solving electromagnetic information security and electromagnetic pollution.In this article,three-dimensional network structure carbon nanofiber aerogels(3DNSCAs)are prepared by vacuum annealing of three-dimensional network structure agarose/zinc acetate obtained by freeze-drying of agarose/zinc acetate gel.The EMWA rubber composites with 2.2%(in mass)3DNSCAs have almost the same density as silicone rubber(PDMS),and the dispersity of 3DNSCAs in PDMS is studied by rheological analysis.The effective absorption bandwidth(EAB,frequency for reflection loss<–10 dB)of the 2 mm thick PDMS/C-800 is 4 GHz,and the minimum value of reflection loss(RL_(min))is−52 dB with the thickness of 3.5 mm.The PDMS/C-1000 with the thickness of 3.5 mm has an EAB up to 4.8 GHz.Radar cross section(RCS)reduction of PDMS/C-800 can achieve 20 dB⋅m2 at the frequency of 6 GHz.

Novel concept of nano-additive design:PTFE@silica Janus nanoparticles for water lubrication

Polytetrafluoroethylene(PTFE)has been widely used as a lubrication additive for reducing friction and wear;however,the hydrophobic nature of PTFE restricts its application in eco-friendly water-based lubrication systems.In this study,for the first time,we designed novel PTFE@silica Janus nanoparticles(JNs)to meet the requirement for additives in water-based lubricants,which have excellent dispersion stability in water attributed to the unique amphiphilic structure.By introducing the lubrication of the aqueous dispersion of the JNs with a concentration of 0.5 wt%,the coefficient of friction(COF)and wear volume were reduced by 63.8%and 94.2%,respectively,comparing to those with the lubrication of pure water.Meanwhile,the JNs suspension also exhibits better lubrication and wear-resistance performances comparing to commercial silica and PTFE suspensions.The excellent tribological behaviors of PTFE@silica JNs as nano-additives could be attributed to the synergetic effect of the two components,where the PTFE provided lubrication through the formed tribofilms on the friction pairs,and the rigid silica further enhanced the wear-resistance performance.Most importantly,the unique structure of JNs makes it possible to use PTFE as an additive in water-lubrication systems.Our study shed light on the design and application of novel JNs nanomaterials as additives to meet the requirements of future industrial applications.

Unleashing the Power of Bio-based Thermotropic Liquid Crystal Modifiers:Toughening and Reinforcing Petroleum-based Epoxy Resin without Compromising Other Properties

Toughening the petroleum-based epoxy resin blends with bio-based modifiers without compromising their modulus,mechanical strength,and other properties is still a big challenge in view of the sustainability.In this study,a bio-based liquid crystal epoxy resin(THMT-E P)with an s-triazine ring structure was utilized to modify a petroleum-based bisphenol A epoxy resin(E51)with 4,4'-diaminodiphenylsulfone(DDS)as a curing agent,and the blended systems were evaluated for their thermal stability,mechanical properties,and flame retardancy.The results showed that the impact strength of the blended system initially increased and then decreased with the increase in THMT-EP content,and it reached the a maximum value of 26.5 kJ/m^(2)when the THMT-EP content was 5%,which was 31.2%higher than that of E51/DDS.Notably,the flexural strength,modulus,and glass transition tem perature of the blended system were all simultaneously improved with the addition of THMT-EP.At the same time,the addition of THMT-EP enhanced the flame retardancy of the system by increasing the char yield at 700℃and decreasing the peak heat release rate and total heat release rate.This work paves the way for a more sustainable improvement in the comprehensive performance of epoxy resin.

A novel reprocessable chloroprene rubber based on dynamic disulfide metathesis

For sustainable application of chloroprene rubber(CR),a new technology is developed by the vulcanization of CR using 2,2'-dithiodipyridine(DPD)as a cross-linking agent with the repro-cessing performance owing to disulfde metathesis.When DPD was incorporated into CR vulcanization,the Menschutkin reac-tion between allyl chloride group and pyridine group occurred with a maximum exothermic peak at 184°C.The number of effective cross-linking bond at o.5 phr DPD vulcanizate was higher than that at high DPD content.This vulcanizate showed high tensile strength(11.12 MPa)and elongation at break(1253±120%)owing to the exchangeable disulfide bond in the system.Under the catalysis of triphenylphosphine,the metathesis of disulfide compound was improved obviously,which endowed CR/DPD vulcanizates with good recyclability performance.Disulfide cross-linkage maintains its stability at low temperature,thus ensuring the mechanical stability of CR/DPD vulcanizate under the ambient conditions.Vulcanization and reprocessing of CR/DPD vulcanizate can be conducted with common industrial rubber processing equipment.Such reprocessable chloroprene rubber could have potential appli-cation in CR industry,also serve to significantly improve envir-onmental sustainability.

Shape Effects of Cylindrical versus Spherical Unimolecular Polymer Nanomaterials on in Vitro and in Vivo Behaviors

To date,how the shape of nanomaterials infuences their biological properties is poorly understood,due to the insufcient controllability of current preparative methods,especially in the shape and size of nanomaterials.In this paper,we achieved the precise syntheses of nanoscale unimolecular cylindrical polymer brushes(CPBs)and spherical polymer nanoparticles(SPNPs)with the same volume and surface chemistry,which ensured that shape was essentially the only variable when their biological performance was compared.Accurate shape efects were obtained.Impressively,the CPBs had remarkable advantage in tissue penetration over the SPNPs.Te CPBs also exhibited higher cellular uptake and rapider body clearance than the SPNPs,whereas the SPNPs had longer blood circulation time,rapider tumor vascular extravasation,and higher tumor accumulation than the CPBs.Additionally,this work also provided a controllable synthesis strategy for nanoscale unimolecular SPNPs by integrating 21 CPBs to a�-cyclodextrin core,whose diameter in dry state could be up to 45 nm.

Ring-opening Polymerization of 2-Oxabicyclo[2.2.2]octan-3-one and the Influence of Stereochemistry on the Thermal Properties of the Polyesters

Polyesters with cyclic structures in the main chain typically possess superior mechanical and thermal properties together with chemical recyclability.Ring-opening polymerization(ROP)of bridged or fused bicyclic lactones is a simple,and in most cases controlled method to synthesize polyesters with alicyclic moieties in the polymer backbone.The stereochemistry of the alicyclic structures has a great effect on the polymer properties,which can be regulated by varying the polymerization conditions.Here,we report a systematic investigation on the ROP of 2-oxabicyclo[2.2.2]octan-3-one([2.2.2]VL)under different conditions.When initiated byn-butyl lithium(n-BuLi)or catalyzed by trifluoromethanesulfonic acid(TfOH)in the presence of benzyl alcohol,P[2.2.2]VLs containing all cis^(-1),4 disubstituted cyclohexane ring were obtained.However,P[2.2.2]VLs initiated by sodium methoxide(MeONa)or catalyzed by organic superbase contained both cis and trans isomeric structural units.The cis to trans transformation mechanism under these conditions was manifested,and the effect of stereochemical variations on the properties ofP[2.2.2]VLwas revealed.The stereoregularP[2.2.2]VLs,bothcisandtrans,exhibited higher crystallinity and melting temperatures(Tm)than those of the stereoirregular isomers.Finally,the degradation of P[2.2.2]VL with acid at high temperature could recover 3-cyclohexenecarboxylic acid.

A hybrid lithium sulfonated polyoxadiazole derived single-ion conducting gel polymer electrolyte enabled effective suppression of dendritic lithium growth

Lithium metal is deemed as an ideal anode material in lithium-ion batteries because of its ultrahigh theoretical specific capacity and the lowest redox potential.However,the rapid capacity attenuation and inferior security resulting from the dendritic lithium growth severely limit its commercialization.Herein a novel hybrid gel polymer electrolyte (GPE) based on electrospun lithium sulfonated polyoxadiazole (LiSPOD) nanofibrous membrane swelled by lithium bis(trifluoromethanesulfonyl)imide (Li TFSI) ether liquid electrolyte is proposed to address the issue of lithium dendrites.The Li-SPOD membrane synthesized by a simple one-pot method exhibits excellent mechanical strength and thermal resistance due to its high molecular weight and rigid backbone.The electron-withdrawing oxadiazole ring and oxadiazole ring-Li;complex,and N,O heteroatoms with lone pairs of electrons in Li-SPOD macromolecular chains facilitate the dissociation of-SO_(3)Li group and Li^(+)transference.The hybrid Li-SPOD GPE exhibits both a high lithium-ion transference number (0.64) and high ionic conductivity (2.03 m S/cm) as well as superior interfacial compacity with lithium anodes.The Li Fe PO_(4)-Li cell using this novel GPE can operate steadily at 2C for 300 cycles,remaining a high discharge capacity of 125 m Ah/g and dendrite-free anode.Remarkable performance improvements for the Li-Li and Cu-Li cells are also presented.

HCAⅡ-inspired Catalysts for Making Carbon Dioxide-based Copolymers:The Role of Metal-hydroxide Bond

The general characteristics of the active center of the catalysts（including zinc-cobalt（III） double metal cyanide complex [Zn-Co（Ⅲ） DMCC]） for the copolymerization reaction of carbon dioxide（CO2） with epoxide are summarized. By comparing the active center, catalytic performance of the Zn-Co（Ⅲ） DMCC（and other catalysts） with HCAII enzyme in the organism for activating CO2（COS and CS2）, we proposed that the metal-hydroxide bond（M-OH）, which is the real catalytic center of human carbonic anhydride Ⅱ（HCAⅡ）, is also the catalytic（initiating） center for the copolymerization. It accelerates the copolymerization and forms a closed catalytic cycle through the chain transfer reaction to water（and thus strictly meets the definition of the catalyst）. In addition, the metal-hydroxide bond catalysis could well explain the oxygen/sulfur exchange reaction（O/S ER） in metal（Zn, Cr）-catalyzed copolymerization of COS（and CS2） with epoxides. Therefore, it is very promising to learn from HCAⅡ enzyme to develop biomimetic catalyst for highly active CO2/epoxide copolymerization in a well-controlled manner under mild conditions.

Non-linear Radical Additions-Coupling Polymerization of Monovinyl Monomers towards Polymer Networks: Theory, Tunability and Heritable Architecture

Exploring new polymerization strategy for current available monomers is a big challenge in polymer science. Here we re-investigate radical polymerization of monovinyl monomer(MVM) initiated by uniform branched polyfunctional initiator(PFI), which is termed non-linear radical additions-coupling polymerization(NLRAs CP). In NLRAs CP, both addition and coupling reactions of radical contribute to the construction of the polymer chains, which leads to continuous growth of branch topology. Theoretical analysis of NLRAs CP predicts that the gelation is determined by the functionality of PFI(a), the extent of initiation of the PFI(q) and the termination factor of radical(φ). NLRAs CPs of styrene and methyl methacrylate promoted by Cu(0)/MeTREN or Mn_(2)(CO)_(10)/visible light were conducted. After the cleavage of incorporated PFI fragment or junctions in the network, the network was transformed to linear chains having almost the same structure as segmental chains in the precursor network. This allows the reverse deducing the network structure from its cleaved products. It has been proven that NLRAs CP includes stepwise initiation of PFI, chain-growth of segmental chains and successive endlinking of macroradicals derived from PFI. The three parameters related to the gelation process, a, q and φ, were adjusted via binary PFI, the feed ratio of [Mn_(2)(CO)_(10)]/[PFI] and addition of non-homopolymerizable comonomer respectively. The minimum values of a and q, and the minimum amount of comonomer required for gelation were determined,which can be applied to estimate φ of various macroradicals. NLRAs CP opens a general and facile strategy for synthesis of a variety of polymer networks with heritable architecture by one-pot polymerization of various MVMs.

Unsymmetric Side Chains of Indacenodithiophene Copolymers Lead to Improved Packing and Device Performance

Two conjugated polymers(PulDTBD and PulDTQ)with un symmetric side chai ns have been prepared for polymer solar cells using two other polymers(PIDTBD and PIDTQ)with symmetric side chains as control compounds.The combi nation of methyl a nd 4-hexylphenyl side chai ns on the same bridged carb on can en sure good solubility,decrease tt-tt stacking dista nces,and bring proper miscibility with PC71BM simultaneously.Therefore,the corresp on ding polymer solar cells(PSCs)based on donor polymers with un symmetric side chains exhibited enhanced short-circuit current density(■)and power conversion efficiency(PCE)compared with those of control polymers.The PIDTBD and PIDTQ based devices possessed low PCE of 2.13%and 1.48%,while PCEs of devices based on PulDTBD and PulDTQ were improved to 3.93%and 4.12%,respectively.The results demonstrate that unsymmetric side chain engineering of conjugated polymers is an effective approach to achieve high performance PSCs.