Polymerization of diacetylenes in multilayers

A series of amphiphilic diacetylene monocarbonic acids was synthesized, and their ability to form monolayers at the air–water interphase was investigated. Acids with total number of C atoms ≥20 and mp >45°C form surface states suitable to be used for buildup of multilayers by the Langmuir–Blodgett technique. Using the LB technique, multilayers of defined thickness were built up on quartz substrates. The multilayers were polymerized by exposure to a UV light source according to the mechanism of solid-state polymerization of diacetylenes without destruction of the layer structure and with retention of the packing in the individual layers. Thus well-defined polymer multilayers were obtained. The monomer and polymer multilayers were characterized by UV spectra, x-ray small-angle diffraction, and interference microscopic and electron microscopic techniques. The polyconjugated backbones of the polymer chains are all stretched out in the plane of the substrate but not over macroscopic dimensions because the multilayers have a crystalline domain structure. The polymer multilayer films are quite stable under ambient conditions.     

聚酰亚胺多层膜的制备及其在非线性光学中的应用

报道了一种通过旋涂制备NLO聚合物多层膜的方法.紫外-可见吸收光谱及膜的厚度表征说明,在所得多层膜的结构中,聚合物单层膜的厚度可以较好地控制在100~200nm之间,所得含有5个双层的NLO多层膜(厚度1.6μm)具有良好的结构均一性,光学显微镜下没有观察到明显的结构缺陷.与单层具有较大厚度的NLO聚合物薄膜(如2~4μm)相比,所得聚合物多层膜可以允许掺杂更多的发色团而不发生相分离.     

Influence of solid-state biaxial orientation on the adhesion between poly(ethylene terephthalate)/tie layer/isotactic polypropylene multilayer films

Current state-of-the-art packaging films typically consist of solid-state stretched multilayer polymer systems, in which each of the polymer layers provides a specific property. Often these polymer film layers are incompatible and need to be glued together by so-called “tie layers.” In this article, we apply a novel biaxial orientation technique to examine the effect of solid-state biaxial stretching on the adhesive behavior of a model multilayer system consisting of poly(ethylene terephthalate) and isotactic polypropylene, as an example of two typical incompatible base layers, glued together by a common tie layer. Two main factors affecting the adhesion, the temperature at which the biaxial stretching is performed and the thickness of the tie layer, are discussed in detail. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 446–454     

Real time evaluation of composition and structure of concanavalin A adsorbed on a polystyrene surface

In situ qualitative and quantitative evaluations of adsorbed submonolayers and multilayers of the protein Concanavalin A (ConA) on a polystyrene surface were carried out by attenuated total reflection infrared spectroscopy. The influence of pH and adsorption time on the composition and structure of the adsorbed protein layers was investigated by comparison of the experimental spectra with simulated spectra of hypothetical multilayer systems with the assumed composition, thickness, and structure. This methodology allows the differentiation of observed spectral changes that result from pure optical effects, associated with the passing of an incident beam through the multilayer system, from the chemical and structural changes caused by physicochemical interactions of proteins with polymer surfaces. This represents significant progress since small variations in the band positions or intensities of amide I and amide II infrared absorbance bands have an important interpretation consequence. The applied methodology significantly reduces the misinterpretation of recorded spectra of protein layers and is rewarded by a deep insight of the structure and composition of the samples. The composition, structure, and kinetics of the adsorption of ConA and hydration level of the adsorbed layers were evaluated in detail. Competitive adsorption of bovine serum albumin on pre-adsorbed ConA layers also was investigated to characterize the ConA surface distribution. Parallel studies using X-ray photoelectron spectroscopy support the conclusions drawn from infrared spectroscopic investigations on ConA molecular distributions at the polymer surface. Two-step models that describe ConA submonolayer formation at pH 4.8 and multilayer formation at pH 7.8 are proposed.     

Polyelectrolyte spin assembly: Influence of ionic strength on the growth of multilayered thin films

Layer-by-layer (LbL) assembly of polymer electrolyte multilayers is now a well-established method for the fabrication of thin films by sequential adsorption of alternating layers of oppositely charged polyelectrolytes. Most commonly, such adsorptions have been from quiescent solutions of varying ionic strength and pH. Here, we report results on an alternative processing route for the achievement of polymeric multilayer assemblies of poly(sodium-4-styrene sulfonate) and poly(allylamine hydrochloride) that utilizes conventional spin coating. We investigated and describe herein the dependence of multilayer film buildup on solution ionic strength for comparison with similar dependence in quiescent adsorption. Using UV-Vis spectroscopy we monitored the growth of the multilayered films, while with Atomic Force Microscopy (AFM) we examined the surface features and measured coating thicknesses at different salt concentrations. AFM and UV-Vis data reveal two regimes of behavior with increasing salt: strong salt-dependence at low salt contents, and weak salt-dependence for high salt contents. To explain this observation, we introduce the relevance of the dimensionless group De = τ, the local Deborah Number, to the problem. As ionic strength increases, τ increases so that spin-assembly flow influences adsorbed conformation, and thus LbL growth rate. Our results indicate the ability to design and control polyelectrolyte multilayered structures prepared via spin assembly by varying solution properties that influence the conformation of deposited polymer chains. Additionally, our studies reveal the need for study of the fundamental mechanisms of polyelectrolyte adsorption within complex flow fields. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3654–3666, 2004     

Solvent‐tunable colors in imprinted helical structures on polymer template via multiple UV‐induced polymerization

A solvent tunable single‐layer polymer film with a multipitched photonic structure as a new photonic band gap material has been developed by imprinting the helical structures on polymer matrices through multiple photocrosslinking in an induced chiral nematic mesophase. Here, the polymer matrices themselves served as a chiral template, which exhibited Bragg reflections in the absence of both a chiral dopant and anisotropic materials because of the memory effects of the polymer network. Tuning of colors was achieved by making a refractive index contrast in the two periodic media of imprinted solid helical structure and the isotropic liquids that fill it. On incorporation of various isotropic liquids in the imprinted matrices, a sharp peak in the reflection spectrum shifted drastically, which indicated that the wavelength shifts strongly depended on the sort of liquids that filled the matrices. The effects of temperature on the imprinted polymer template feeding the various liquids were studied through the reflectance spectra. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Defect-free polymer multilayers prepared via chemoselective immobilization

In this paper, we investigated electrochemical properties of polymer multilayers on gold substrates using impedance spectroscopy. The multilayer was prepared by chemoselective ligation between aldehyde- and oxyamine-functionalized polymers via a layer-by-layer approach. The impedance spectra in a buffer solution in the absence of redox species revealed the formation of highly impermeable and defect-free films. The dielectric thickness of the polymer film, which is proportional to the reciprocal of capacitance, linearly increased as the number of deposition layer increased. The defect area of the polymer multilayer was obtained using the faradaic impedance with redox species. The surface coverage of eight polymer layers was determined to be 99.99%. Thus, the layer-by-layer deposition via chemoselective ligation offers a new way to prepare a highly insulating and defect-free polymer layer with finely tunable capacitance as a function of the number of deposition layers.     

Brillouin light scattering studies of the mechanical properties of polystyrene/polyisoprene multilayered thin films

We have used Brillouin light scattering (BLS) to investigate the mechanical properties of thin polystyrene (PS) and polyisoprene (PI) films incorporated in a multilayer geometry consisting of alternating layers of the two polymers. All samples had a total thickness h ∼ 1600 Å, and consisted of between 2 and 10 individual polymer films; individual layer thicknesses were as small as 160 Å. Ellipsometry was used to determine the thickness of the PS and PI layers. The velocities of several high-frequency film-guided mechanical waves were measured using BLS and the results are compared with values calculated using an effective medium approach. The effective elastic constants of the multilayered films were obtained from those determined for thick films of PS and PI. Remarkable agreement was obtained between the measured and calculated velocities even for samples in which the individual layer thicknesses were much less than the unperturbed size of the polymer molecules. These results suggest that the mechanical properties of polymers change very little even when the molecules are forced into highly confined geometries. © 1996 John Wiley & Sons, Inc.     

Melt-processed polymer multilayer distributed feedback lasers: Progress and prospects

Reflecting recent progress in the functionalization of roll-to-roll processed polymer multilayers, this review describes the development and characterization of versatile large-area multilayer distributed feedback (DFB) lasers. These developments are reviewed in the broader context of microresonator lasers, with a brief tutorial on the theory and experiment needed to understand their unique features. Of particular interest is the broad tunability of these DFB lasers by simple modification of their structure, mechanical stretching, and temperature. Prospects for commercialization of polymer multilayer DFB lasers are also discussed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 251–271     

The electroactive multilayer films of polyelectrolytes and Prussian blue nanoparticles and their application for H2O2 sensors

Prussian blue (PB) nanoparticles were immobilized in polyelectrolyte (PE) multilayers of various compositions and thickness. Films containing nanoparticles and poly(allylamine hydrochloride) (PAH) were formed using the layer-by-layer adsorption method. A layer of branched poly(ethyleneimine) (PEI) was used to anchor the multilayer structure at the surface of a gold electrode. The films exhibited electroactive properties, increasing with the number of deposited PB layers. The properties of PEI/(PB/PAH) _n multilayers were then compared with the ones containing additionally the conductive polymer poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS). We found that the addition of the conductive, water-soluble polymer enhances the electroactive properties of the multilayer films. It also increased sensitivity of the multilayer-covered electrodes for electrochemical detection of hydrogen peroxide.     

A study of the optical properties of polypropylene based polymer composite films

The optical clarity of the polymeric material can be influenced by changing the preparations parameters and thus the polymer structure. In this study, the transmittance, absorptance and reflectance of the polypropylene (PP) based polymer composites, synthesized by pressing method, changing the thickness between 8 — 29 μm, are investigated. Infrared and ultraviolet spectra of PP/diamond and PP/fiber composite in the wavelength range 200–25000 nm are examined. Optical absorption spectra recorded in the UV-Visible range are presented; the determined values of energy gaps are listed. The results indicate that both mechanism, direct and indirect transitions may exist. The analysis of absorption peaks corresponding to oxygen groups, for PP/diamond (0.3–0.5 %) and PP/fiber (20–30 %) composites, show low optical densities which complies with our other studies.     

Effect of molecular weight and temperature on physical aging of thin glassy poly(2,6-dimethyl-1,4-phenylene oxide) films

The effects of polymer molecular weight and temperature on the physical aging of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is examined. Gas permeability and refractive index were monitored during the aging process for PPO film samples at three aging temperatures below the glass transition temperature. Comparisons between the two samples of PPO that differ widely in molecular weight reveal an insignificant difference, which support the notion that above a critical molecular weight range there is little influence on aging rate. Increased temperature, over the limited range of 35–55 °C, results in higher aging rates for films made from both PPO materials. The rate of aging decreases strongly with increasing film thickness over the range examined, ∼0.4–25 μm. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1390–1398, 2007     

Low band gap copolymers consisting of porphyrins,thiophenes, and 2,1,3‐benzothiadiazole moieties for bulk heterojunction solar cells

Two novel low band gap conjugated copolymers containing porphyrins, thiophenes, and 2,1,3‐benzothiadiazole ( BTZ ) moieties were synthesized and applied in bulk heterojunction solar cells. The thermal, optical, electrochemical, and photovoltaic properties of the two copolymers were examined to investigate the effect of the introduction of BTZ moiety in the backbone of the porphyrin polymers. The copolymers exhibited good thermal stability and film‐forming ability. The absorption spectra indicated that the BTZ moiety has significant influence on the UV–visible region spectra of the copolymers: with increasing the molar amount of BTZ moieties in conjugated main chain, the absorption in the range of 450–700 nm is largely broadened and red‐shifted compared to the similar polymers without BTZ moiety, and the optical band gaps of copolymers were narrowed to ～1.50 eV. The photoluminescence spectra showed that there is effective charge transfer in the whole conjugated main chain. Cyclic voltammetry displayed that the band gaps were reduced effectively by the introduction of the BTZ moieties. The bulk heterojunction solar cells were fabricated based on the blend of the copolymers and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) in a 1:2 weight ratio. The maximum power conversion efficiency of 0.91% was obtained by using P2 as the electron donor under the illumination of AM 1.5, 100 mW/cm². © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

带隙可调各向同性蛋白石光子晶体的制备与研究

用旋涂法将聚苯乙烯微球组装成光子晶体,研究了此光子晶体的特点,并分析了在单一微球粒径下旋涂参数对光子带隙的影响.结果表明:旋涂法制备的光子晶体具有各向同性特点,其光子带隙由旋涂参数决定.光子晶体的反射波段取决于乳液中微球的质量分数,而反射强度取决于旋涂层数.因此,在设计光子晶体时,可以根据需要,通过微球的质量分数和旋涂...     

Unusual collapse of highly hydrated polyelectrolyte multilayers with the ionic strength

Highly hydrated polyelectrolyte multilayers (PEMs) were fabricated by “layer by layer” (LBL) assembly of poly (diallyl dimethyl ammonium chloride) (PDADMAC) and poly (sodium 4‐styrene sulfonate) (PSS) in 0.5 M NaCl. Both thickness and hydration of the film were determined in situ as the multilayer was assembled by means of the quartz crystal microbalance with dissipation (QCM‐D) and the Spectroscopic Ellipsometry techniques combined in a single device. For PEMs of 17 total layers in water, a final thickness of up to 300 nm and a hydration of 69% were measured. The response towards the ionic strength was then studied by means of QCM‐D. PEMs of 17 layers, with PDADMAC as last layer, shrunk dramatically and lost water when exposed to aqueous NaCl solutions of increasing concentration. Indeed, a thickness variation up to 100 nm and reduction in the 50% of the water content were observed when the PEM was exposed to 1 M NaCl. On the contrary, PEMs where PSS appears on top showed no measurable change upon the variation in the ionic strength. This brings the possibility to control the responsive character of the PEMs simply by selecting the last polyelectrolyte layer (PDADMAC or PSS) deposited. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Focused ion beam micromachining and computation of polymeric photonic band gap

This article introduces a new approach to the achievement of low cost devices for optical telecommunications. For this purpose, the implementation of polymer components and of the WDM method show several advantages. A polymeric photonic band gap lattice can effectively assume demultiplexing at the wavelength of 1.55 μm without energy dissipation. First, the computation of the geometrical parameters designing a polymer photonic crystal by means of the finite‐difference‐time‐domain method, implemented with Bloch functions, is presented here. Second, the achievement of 2D polymer lattices by a dry process, the focused ion beam milling, is exposed. The experimental conditions for the achievement of a master are discussed on the basis of the milling performances and of the polymers physical properties. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2993–3002, 2007     

Monolayer and multilayer compact film formations on different substrates by physical deposition

Dissipative particle dynamics simulations are applied to investigate the monolayer and multilayer film formations on different solid substrates by physical deposition. The influences of the polymer concentration, the polymer chain length, the solvent quality, and the interactions between the polymer solution and the solid substrate surface on the film formation dynamics and the mechanism are studied in detail. The results are analyzed in terms of the thickness and the shape of the deposited film, the kinetics of phase separation in the polymer solution, and the contact angle formed between the polymer aggregations and the substrate surface. Moreover, we suggest two strategies, designing a deposition process analogous to “chemical titration” and physically blocking interlayer diffusion by a simple crosslinked network barrier, to deposit the compact monolayer and multilayer films with better quality, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 353–365, 2009     

Controlled growth of metallic inverse opals by electrodeposition

The kinetics of nickel electrodeposition through a template of ordered polystyrene spheres is addressed experimentally and applied to prepare a series of metallic inverse opals with a non-integer number of layers. The observed layer-by-layer growth is discussed in terms of subsequently increasing disorder of the growth front. Reflection and transmission spectra of the samples demonstrate that the key optical features of these photonic crystals are most pronounced when the thickness does not essentially exceed two layers. The intensities and band positions can be additionally tuned by varying the height of the metal coating continuously, not discretely. These findings are confirmed semi-quantitatively by means of computational modeling of the spectra. Specific deposition current transients for in situ control of geometric parameters are discussed.     

Sensitivity of transmission surface plasmon resonance (T-SPR) spectroscopy: self-assembled multilayers on evaporated gold island films

The distance dependence of the localized surface plasmon (SP) extinction of discontinuous gold films is a crucial issue in the application of transmission surface plasmon resonance (T-SPR) spectroscopy to chemical and biological sensing. This derives from the usual sensing configuration, whereby an analyte binds to a selective receptor layer on the gold film at a certain distance from the metal surface. In the present work the distance sensitivity of T-SPR spectroscopy of 1.0-5.0 nm (nominal thickness) gold island films evaporated on silanized glass substrates is studied by using coordination-based self-assembled multilayers, offering thickness tuning in the range from approximately 1 to approximately 15 nm. The morphology, composition and optical properties of the Au/multilayer systems were studied at each step of multilayer construction. High-resolution scanning electron microscopy (HRSEM) showed no apparent change in the underlying Au islands, while atomic force microscopy (AFM) indicated flattening of the surface topography during multilayer construction. A regular growth mode of the organic layers was substantiated by X-ray photoelectron spectroscopy (XPS). Transmission UV-visible spectra showed an increase of the extinction and a red shift of the maximum of the SP band upon addition of organic layers, establishing the distance dependence of the Au SP absorbance. The distance sensitivity of T-SPR spectroscopy can be varied by using characteristic substrate parameters, that is, Au nominal thickness and annealing. In particular, effective sensitivity up to a distance of at least 15 nm is demonstrated with 5 nm annealed Au films. It is shown that intensity measurements, particularly in the plasmon intensity change (PIC) presentation, provide an alternative to the usually measured plasmon band position, offering good accuracy and the possibility of measuring at a single wavelength. The present distance sensitivity results provide the basis for further development of T-SPR transducers based on receptor-coated Au island films.     

Morphological reorganization and mechanical enhancement in multilayered polyethylene/polypropylene films by layer multiplication or mild annealing

Shortly after processing, Polyethylene/Polypropylene (PE/PP) multilayer films demonstrate an increase in tensile modulus and other mechanical properties when the individual layer thickness is below 0.5 µm. Subsequent annealing at 60 °C for 16 h brings the properties of all other samples to similar values. WAXD characterization of the layered films identified a prevalence of mesophase in the thicker PP layers. In samples with increased layer numerosity or subjected to annealing, WAXD detected its conversion to α crystalline phase that correlates with improved mechanical properties. SSNMR and DSC detailed the defective nature of α iPP crystallites. Comonomers, detected by NMR in the commercial polymers used for the films, are the source of “tunable disorder” that dictates the formation of the PP mesophase and the low temperature of conversion to the mechanically stronger defective α phase. Soft intrafilm layer interfaces instead enable nucleation and localized polymer chain rearrangement even without annealing. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 520–531