Effect of temperature on the selection of semiconducting single walled carbon nanotubes using Poly(3-dodecylthiophene-2,5-diyl)

We report on the investigation of the temperature effect on the selective dispersion of single-walled carbon nanotubes (SWNTs) by Poly(3-dodecylthiophene-2,5-diyl) wrapping. The interaction mechanism between polymer chains and SWNTs is studied by controlling the polymer aggregation via variation of the processing temperature. Optical absorption and photoluminescence measurements including time resolved photoluminescence spectroscopy are employed to study the degree of interaction between the polymer in different aggregation states and the carbon nanotubes. At low processing temperatures, results are consistent with the planarization of the polymer chains and with SWNTs working as seeds for polymer aggregation. The formation of small clusters due to the inter-digitation of alkyl tails between neighboring polymer-wrapped SWNTs allows the formation of the SWNT bundles, as experimentally evidenced and investigated by molecular dynamics simulations. The interaction between the tubes within the bundles, which is reflected in the variation of the photoluminescence dynamics of the polymer, can be suppressed by warming up the sample.     

Aggregation in Langmuir and Langmuir-Blodgett films of azopolymers and its role for optically induced birefringence

Aggregation in azopolymers is reported to affect the Langmuir monolayer characteristics and the optically induced birefringence of Langmuir-Blodgett (LB) films from DR19 isophorone polyurethane (PIPDI) and DR19 4,4′ diphenylmethane polyurethane (PMDI). In mixed monolayers with cadmium stearate (CdSt), the folding of PMDI molecules appears to be substantially changed compared to the monolayer of the pure polymer, leading to a surface potential that is higher than observed for monolayers of pure PMDI and of pure CdSt. UV-Vis spectroscopy data of the deposited mixed LB films indicate H-type aggregation for PMDI/CdSt, in contrast to PIPDI/CdSt and other azopolymers investigated earlier. The H-type aggregation precludes photoisomerization, thus requiring a higher laser power for the maximum induced birefringence to be achieved in LB films of PMDI/CdSt.     

Dye aggregation and interaction of dyes with a water‐soluble polymer in ink‐jet ink for textiles

Detailed understanding of the interaction between dyes and additives and the aggregation behaviour of the dye molecules in aqueous solutions is required to develop ink‐jet ink for textiles. In the present study, the aggregation behaviour of three acid dyes (CI Acid Red 88, CI Acid Red 13 and CI Acid Red 27) containing different number of sulphonate groups in aqueous solutions was investigated by means of visible absorption spectroscopy. As a result, the higher the solubility of the dyes in water (the larger the number of sulphonate groups in the dyes), the lower are the aggregation constants of the dyes. For all the dyes, the aggregation constants decreased with increasing temperature, indicating the exothermic process of the dye aggregation. The thermodynamic process for CI Acid Red 88 with one sulphonate group is less enthalpic and more entropic than that for CI Acid Red 13, which contains two sulphonate groups. CI Acid Red 27, which includes three sulphonate groups, hardly forms any aggregates. To elucidate the effects of the polymer additive, the binding constants of the dyes with the water‐soluble polymer, poly(vinylpyrrolidone) and the aggregation constants of the dyes in aqueous polymer solutions were also estimated. In addition, the binding constants were influenced by the number of sulphonate groups in the acid dyes: the larger number of sulphonate groups diminished the binding constants. The aggregation constants in the presence of poly(vinylpyrrolidone) were smaller than those in its absence at every temperature for all dyes. This suggests that poly(vinylpyrrolidone) has disaggregation effects. Furthermore, poly(vinylpyrrolidone) makes the aggregation process less enthalpic with a greater entropic change. Thus, the aggregation process of the dyes in the polymer solutions is thermodynamically different from that in water, reflecting the interactions between the dyes and the polymer.     

Laser annealing and surface modification of plasma polymer-metal composite films

Plasma polymer films with encapsulated metal particles were prepared by simultaneous plasma polymerization and metal evaporation. Laser annealing (Nd-YAG, 1064 nm) causes dramatic changes in the particle size and shape without material ablation, but with changes in the surface topography. This results in changes in the optical plasma resonance absorption, as demonstrated by UV-visible-near-infrared (NIR) spectroscopy. The invariable transmission in the UV region of the plasma polymer matrix after laser annealing confirms that there is no material ablation. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) demonstrated particle size changes and modifications of the plasma polymer surface due to laser annealing.     

Aggregation behaviour of stereoregular poly(methyl methacrylates) in dilute solution: light scattering and proton n.m.r. study

The aggregation behaviour of syndiotactic and isotactic poly(methyl methacrylate) in methyl ethyl ketone, n-butyl acetate, and 2-ethoxyethanol was investigated by light scattering and ¹H n.m.r. spectroscopy. Syndiotactic poly(methyl methacrylate) remains in its molecular form in solution at temperatures above 60°–70°C; on cooling it undergoes aggregation followed by macroscopic separation (precipitation) of the polymer from solution. The rate of these processes depends on temperature, concentration of the polymer, and solvent. Molecular solutions of isotactic poly(methyl methacrylate) can be prepared only by long-term heating at temperatures above 100°–130°C. During cooling, isotactic macromolecules prior to separation form stable associates in the region limited by discrete temperatures, and below this region polymer precipitates. The individual stereo forms of poly(methyl methacrylate) are separated from solution at different temperatures which are above the θ-temperatures of the atactic polymer.     

星状支化PS的合成与表征

利用原子转移自由基聚合方法,以α-溴代苯乙烷为引发剂,CuBr／2,2'-联二吡啶作为催化体系,合成星状支化聚苯乙烯(PS)。引发二苯甲烷双马来酰亚胺／苯乙烯电荷转移络合物体系就地优先生成多官能团引发剂,再引发苯乙烯聚合。采用核磁共振、凝胶渗透色谱、多角度激光散射和特性黏数等分析方法对聚合过程、聚合物结构、聚合物相对分子质量及其分布进行分析与表征。由多角度激光散射法测定的绝对重均分子量是由凝胶渗透色谱测定的4倍左右,相同相对分子质量的线型PS的特性黏数是星状PS的20倍,证实聚合产物确实具有支化结构。     

Supramolecular structures of an amphiphilic hairy-rod conjugated copolymer bearing poly(ethylene oxide) side chain

The structures of an amphiphilic conjugated graft copolymer, poly(2,3-diphenyl-5-(trimethylene-heptadeca(oxyethylene)-methoxy-phenylene vinylene) (denoted as PVEO₁₇) composing of a conjugated DP-PPV backbone and PEO side chains, in bulk and solutions with tetrahydrofuran (THF) and water have been investigated by small-angle X-ray scattering (SAXS). In bulk state, the DP-PPV main chains in PVEO₁₇ stacked to form flat disk microdomains dispersed in the PEO side-chain matrix. The corresponding wide angle X-ray scattering pattern revealed the existence of crystallinity of the PEO side chains. The structure of the polymer in solution was affected by the solvent quality and the polymer concentration. PVEO₁₇ chains were relatively well dispersed in THF. In aqueous solutions, however, the amphiphilic PVEO₁₇ chains aggregated significantly over the concentration range of 1–8 wt%, where the polymer was found to self-organize to form cylindrical micelles with the aggregation number increasing with the increase of concentration. The photophysical properties characterized by UV–Vis and photoluminescence spectroscopy were strongly affected by the aggregation state of the polymer.     

Spectroscopic studies of spin-coated dye-in-polymer films. On the relationship between compatibility and aggregation of small molecules in polymer matrices

Dye-in-polymer (DIP) films of various concentrations of I (a p-N,N-dialkyl-aminobenzylidenemalononitrile derivative) in four polymers of different dye-polymer compatibilities have been prepared by spin-coating technique using a wide range of coating speeds (600–8000 rpm). The aggregation of dye molecules in polymer matrix was studied by electronic spectroscopy. The dye-polymer compatibility of various DIP systems was examined by d.s.c. Our results indicate that there exists a staturated concentration of I in each polymer and this saturated concentration decreases as the dye-polymer compatibility decreases, e.g. it decreases from ～20% in poly(vinyl acetate) and in poly(isobutyl methacrylate) to ～10% in styrene/isobutyl methacrylate (8:2) copolymer to ～5% in polystyrene. At dye concentrations lower than this saturated concentration, the degree of dye aggregation is not sensitive to varying spin-coating speeds. At dye concentrations higher than this saturated concentration, the degree of dye aggregation depends on the degree of dye-polymer incompatibility and on the spin-coating speed. The significance of the present work in solvent coating technology of small molecule/polymer systems, in general, will be discussed. Finally, the T_g's of various DIP systems were found not to correlate with the dye concentration (by weight). This is attributable to the strong dye-dye interaction of I inside the polymer matrix.     

Alkanol-Induced Micelles of a Very Hydrophilic EO–PO–EO Block Copolymer: Characterization by Spectral and Scattering Methods

The aqueous solution behavior of a PEO–PPO–PEO block copolymer (EO₁₀₃PO₃₉EO₁₀₃), was investigated in the presence of aliphatic alkanols (C₂, C₄, C₆ and C₈). The non-associated polymer chains remain extremely hydrated in water, but aggregation in the form of spherical micelles was evidenced, triggered by the interaction of polymer chains with hydrophobic alkanol. We assume that the hydrophobic interaction between the PPO block of the copolymer and alkanol promotes micellization, which increases further with the introduction of higher chain length species. The critical micellization temperature (CMT), as measured by UV–visible spectroscopy, indicates an interaction of polymer chains with the alkanol bearing a higher chain length, which triggers aggregation. The micelles were characterized by small angle neutron scattering to elucidate the size and related micellar parameters. The gradual increase in the alkanol content increases the aggregation number, though the micelles were spherical in shape. We conclude that ethanol, due to its preferential solubility in the aqueous phase, does not affect the aggregation. The alkanols with chain lengths of C₄–C₈ chain, interact with the PPO block through hydrophobic interaction and shifts the CMTs to lower values. The combined effect of inorganic salt (NaCl) and alkanols show enhanced micellar properties.     

聚醚与长链烷烃共改性硅油的研究及应用*

采用含氢硅油（PHMS）、烯丙基聚醚（FB1000）与不同质量的丙烯酸十八酯（SA）制备了系列具有侧链结构的高分子表面活性剂（PSA）。利用红外光谱（FT-IR）、核磁（NMR）、凝胶渗透色谱仪（GPC）、表面张力、动态激光光散射仪（DLS）、荧光光谱 (FLD)对产物的结构与溶液性质进行了表征和研究。结果表明随着SA含量的增加,聚合物越易聚集缔合形成胶束,粒径从71.40nm增加到141.07nm,粒度分散系数（PDI）增大至0.396,随着疏水基团的增加,溶液表面张力降低至24.20mN/m,临界胶束浓度(cmc)下降至0.49g/L。荧光光谱表明,聚合物溶液浓度增大到一定值时,溶液中会形成疏水微区,第一第三发射峰的比值（I1/I3）不断减小,达到临界缔合浓度（cac）后,芘分子会增溶到胶束中I1/I3趋于稳定。破乳实验结果表明,聚合物PSA的破乳脱水率达93%。     

Comprehensive study of polymer fiber surface modifications Part 1: high‐fluence UV‐excimer‐laser‐induced structures

Recently, there has been great interest in physico‐chemical surface treatments for modifying polymer surfaces. Ultraviolet (UV)‐excimer‐laser irradiation of polymers is of particular interest. In this study, polyamide was irradiated by a 193 nm excimer laser with a fluence above its ablation threshold (high‐fluence). Morphological changes of the resulting samples were characterized by scanning electron microscopy (SEM) and tapping mode atomic force microscopy (TM‐AFM). Chemical modifications by laser treatment were studied by X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and chemical force microscopy (CFM). Topographical results indicated that ‘ripple‐like’ structures of micrometer size were formed after laser irradiation. XPS and Tof‐SIMS results showed that bond scission occurred on the polymer surface under the action of high‐fluence. Changes in surface chemical properties of the laser‐irradiated polyamide were supported by CFM experiments. Copyright © 2004 Society of Chemical Industry     

Photochemical reactions in a commerical poly(ether sulfone)

A commercial poly(ether sulfone) has been examined by electronic spectroscopy, continuous photolysis, and laser flash techniques. The spectroscopic experiments indicate that the chromophoric species primarily responsible for light absorption in the region 290–350 nm is the diphenyl sulfone unit. The laser flash experiments give direct evidence of bond scission at the ether linkage on the polymer backbone.     

纤维素基高分子表面活性剂的合成及性能表征

以聚合度为280的纤维素为原料,通过两步反应,制备了纤维素基高分子表面活性剂纤维素棕榈酰酯硫酸钠,利用红外光谱、动态接触角测定仪、透射电镜和动态光散射等对产物的结构和性能进行了表征.结果表明,该纤维素两亲高分子的临界聚集含量为0.60%(质量分数),对应的表面张力为57 mN/m;当水溶液浓度在临界聚集含量附近时,即水溶液的质量分数由0.5%增大到1.0%,胶束的平均粒径由388.0 nm增大到549.7 nm,此时表面活性剂分子已不断聚集成胶束或胶团;此外该类表面活性剂还具有高分子特有的流变性.     

Micelles formation of polystyrene-co-poly (N-acryloylthymine) and its aggregation behavior induced by triple hydrogen bonding

Micelles of a new amphiphilic copolymer bearing pendant thymine groups, polystyrene-co-poly (N-acryloylthymine) (PS-co-PAT), were prepared in aqueous solutions. Transmission electron microscopy and laser light-scattering studies showed that the resultant spherical micelles were nanoscale with narrow size distribution. Moreover, ratio of hydrophilic and hydrophobic contents strongly influenced the hydrodynamic radius of the spherical micelles (113–227 nm). Upon exposure of the PS-co-PAT micelles to melamine, triple hydrogen bonding recognition between melamine and thymine resulted in the aggregation of polymer micelles, and the blue phase transparent solution of the polymer micelles was accordingly changed to turbid emulsion. The aggregation of micelles and hydrogen-bonding interaction between melamine and the PS-co-PAT shell was further confirmed by ¹H NMR spectra and zeta-potential measurements. These results suggested that PS-co-PAT micelles could be a potential new vehicle for melamine recognition.     

A simple and environmentally friendly method for surface modification of ZrO2 nanoparticles by biosafe citric acid as well as ascorbic acid (vitamin C) and its application for the preparation of poly(vinyl chloride) nanocomposite films

In this investigation, poly(vinyl chloride) (PVC) as one of the most important thermoplastic polymer was combined with different concentrations (4, 8, and 12 wt%) of ZrO₂ nanoparticles (NPs) with the purpose of preparing novel nanocomposites (NCs). To prevent aggregation and obtain homogeneous dispersion of the NPs in the polymer matrix, surface modification of ZrO₂ was performed by biosafe, biodegradable as well as biocompatible modifiers such as citric acid and ascorbic acid (vitamin C) due to their ability to form chelates with metal oxides. The effect of modified ZrO₂ on the properties of the PVC was studied by different techniques. The field emission scanning electron microscopy and transmission electron microscopy results indicated that the modified NPs were dispersed homogeneously in the polymer matrix. UV–Vis spectroscopy was used to study optical behaviors of the obtained NCs. Thermogravimetric analysis indicated that the thermal stability of the polymer was enhanced after incorporation with NPs. Finally, mechanical test was revealed that the NC films were more flexible when compared with the neat polymer. POLYM. COMPOS., 38:1756–1765, 2017. © 2015 Society of Plastics Engineers     

Preparation and characterization of thin organosilicon films deposited on SPR chip

The paper reports on the preparation and characterization of organosilicon thin polymer films deposited on glass slides coated with 5 nm adhesion layer of titanium and 50 nm of gold. The polymer was obtained by the decomposition of 1,1,3,3-tetramethyldisiloxane precursor (TMDSO) premixed with oxygen induced in a N₂ plasma afterglow using remote plasma-enhanced chemical vapor deposition (PECVD) technique. The film thickness was controlled by laser interferometry and was 9 nm. The chemical stability of the gold substrate coated with the organosilicon polymer film (p-TMDSO) was studied in different acidic and basic solutions (pH 1-14). While the gold/polymer interface showed a high stability in acidic media, the film was almost completely removed in basic solutions. The resulting surfaces were characterized using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), water contact angle measurements, cyclic voltammetry, and surface plasmon resonance (SPR).     

Validation of mass‐transfer model for VIPS process using in situ measurements performed by near‐infrared spectroscopy

Combined experimental and modeling approaches were performed in order to investigate the influence of formulation and process parameters on mass transfers during VIPS process, using the water/N‐methyl‐pyrrolidone (NMP)/poly(ether imide) (PEI) system. The experiments were conducted using a thick polymer solution at increasing polymer concentrations for various operating conditions. The global water intake rate in the bulk solution was determined by gravimetric measurements (global), and insitu measurements were conducted by near‐infrared spectroscopy at three points in the solution. In parallel, a fully predictive model was developed for predicting mass‐transfer phenomena involved during the VIPS process. The comparison between experimental data and numerical predictions exhibited a good agreement for moderate polymer concentration, but for higher polymer concentrations, the model overestimated the nonsolvent‐transfer rate. This result was explained by the aggregation process of the polymer chains due to water intake. The numerical predictions were improved by modifying the average hole‐free volume expression. © 2012 American Institute of Chemical Engineers AIChE J, 59: 671–686, 2013     

Synthesis and thermal characterization of new dumbbell shaped POSS/PS nanocomposites: Influence of the symmetrical structure of the nanoparticles on the dispersion/aggregation in the polymer matrix

A series of three novel dumbbell shaped polyhedral oligomeric silsesquioxanes (POSS)/ polystyrene (PS) nanocomposites, at different POSS contents (3%, 5% and 10% w/w), was synthesized and characterized in order to investigate the effects of this new bridged structure on the filler‐polymer interaction and then on the thermal behavior of the obtained polymer nanostructured materials (PNMs). Nanocomposites were synthesized by in situ polymerization of styrene and the actual POSS concentration in the obtained PNMs was checked by ¹H NMR spectroscopy. Scanning electron microscopy (SEM) and FTIR spectroscopy evidenced, at the same time, the presence of filler‐polymer interactions and auto‐aggregation phenomena. Degradations were carried out into a thermobalance, in the scanning mode, at various heating rates in both inert and oxidative atmospheres. The characteristic parameters of thermal stability, namely temperature at 5% mass loss and the apparent activation energy of degradation, for the various nanocomposites were determined and an increase in the initial decomposition temperatures of PNMs with increasing the POSS contents was observed. The results are discussed and interpreted. POLYM. COMPOS., 36:1394–1400, 2015. © 2014 Society of Plastics Engineers     

Waterborne acrylic–polyaniline nanocomposite as antistatic coating: preparation and characterization

An antistatic and electrically conductive acrylic–polyaniline nanocomposite coating was successfully synthesized by interfacial polymerization of aniline in the presence of acrylic latex. The acrylic latex was prepared through emulsion polymerization, and aniline was polymerized by in situ interfacial polymerization at the interface of acrylic latex/chloroform phase. Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy and CHNS elemental analysis revealed the existence of 6.24 wt% emeraldine salt of polyaniline (PAni) in the dried film of the nanocomposite. Scanning electron microscopy (SEM) confirmed the presence of colloidal polymer particles in the aqueous phase which was confirmed to have some advantages, including prevention of aggregation of particles, dispersibility improvement and enhancement of the PAni nanofibers aspect ratio in the acrylic polymer matrix. According to SEM results, PAni fibers with the length ranging from 12 to 67 µm and diameters between 0.078 and 1 µm, highly dispersed in the acrylic polymer matrix, were successfully synthesized. Thermal, electrical and mechanical properties of the acrylic copolymer were significantly affected by PAni incorporation. The onset degradation temperature in thermogravimetric analysis revealed that the thermal stability of the nanocomposite was improved compared to that of the pure acrylic copolymer. The nanocomposite film showed electrical conductivity of about 0.025 S/cm at room temperature, along with satisfactory mechanical properties, attractive as an antistatic material in coating applications.     

丙烯酸-马来酸水相共聚合过程中的粒径变化研究

以氧化-还原引发剂Na2 S2O8/Na2S2O5引发丙烯酸-马来酸的水相共聚合,用激光光散射粒径分析仪对共聚合过程中的粒径变化进行了研究.结果表明,体系的平均粒径受聚合物链增长和聚合物链间聚结的影响,随着反应进行而增大.通过分析粒径曲线发现,在加料反应阶段,粒径在100 nm以下的粒子始终保持一定数量,同时周期性地形成粒径在100 nm以上的粒子.