Changes In Polymer Structure Research Articles

Influence of reaction time on the structure of polyaniline synthesized on a pre-pilot scale

Abstract The aim of this work is to follow the structural variations of polyaniline (PAni) obtained by chemical oxidation on a pre-pilot scale, with different reaction times. Synthesis of PAni is well known, but when it is carried out on a pre-pilot scale, several factors can lead to structural changes and understanding these changes is important to improve controls on the synthesis process. The polymers formed were characterized by spectroscopic techniques (Raman spectroscopy, Fourier Transform Infrared - FTIR and UV-Visible). Degree of oxidation and yield were calculated for each reaction time. The analysis by FTIR, the calculated degree of oxidation and the yield showed significant changes in polymer structure at reaction times of 65 and 80 min. This result was attributed to the excessive oxidation of PAni, with the breaking of its polymer chain. The changes observed in the structure of PAni gave subsidies to the optimization of the process of obtaining polyaniline by chemical synthesis.

Image analysis as a useful tool for fast detection of dimensional and structural changes of poly(ethylene terephthalate) containers

The aim of this paper is to present image analysis as a useful technique for fast, reliable and non-destructive detection of dimensional and structural changes in polymers. The possibility of applying image analysis was demonstrated in the case of solvent-induced crystallization of poly(ethylene terephthalate) (PET) containers filled with commonly used organic solvents: chlorobenzene, isophorone, xylene, Espesol, Shellsol A 100, Solvesso 150, propylene glycol, glycerin and water and subjected to the storage stability test at 54 ?C for 14 days (CIPAC 1-MT 46.1.3). In addition, the obtained results were analyzed using one-step analysis of variance (ANOVA) combined with the Duncan?s statistical test (p<0.05). According to the achieved results, three main impacts of the presented paper could be distinguished: 1) dimensional and transparency changes could be precisely followed by image analysis in both following cases: for small changes in water, as well as for significant ones in chlorobenzene; 2) a correlation between the changes in the degree of crystallinity and transparency could be obtained without the continuous material testing by DSC; 3) image analysis is potentially applicable for assessment of other crystalline polymers.

Changes in chemical composition and structure of root cell wall of citrus rootstock seedlings in response to boron deficiency by FTIR spectroscopy

ABSTRACTBoron (B) is an essential microelement for higher plants, and plays a role in cell wall formation. Citrange seedlings with different amounts of B were studied through Fourier-transform infrared spectroscopy (FTIR) analyses. The results showed that the growth and development of new roots were evidently inhibited by B deficiency. Boron-deficiency significantly increased cell wall biomass (CWB) as a percentage of root fresh weight and the ratio of B concentration in cell wall to the total B in roots. The findings from CWB FTIR spectra showed the band at 3429 cm−1 under control condition was shifted to 3442 cm−1 after being B deprived, suggesting that the mode of hydrogen bonding was changed by B deficiency. Boron deficiency clearly decreased the peak height of carboxylic ester band around 1741 cm−1, but increased that of COO− stretching band around 1400 cm−1, suggesting that the relative amount and degree of esterification of carboxylic groups was decreased and pectin content and structure was altered. These results demonstrate that changes in amount, structure, and assembly of root cell wall polymers may be either specific or adaptive responses of citrange seedlings to B deficiency and FTIR can be an appropriate method to study changes in cell wall under B deficiency.

Abnormal gelation phenomenon of Class G oil well cement incorporating polycarboxylic additives and its countermeasures

Cementing security is endangered by the abnormal gelation phenomenon of cement slurry incorporating polycarboxylic additives occurred around 120°C. The differences between gelatinous and non-gelatinous sections were investigated through various techniques. The polymer structural change around 120°C could explain the abnormal gelation phenomenon by viscosity-temperature characterization. The other reasons are the polycarboxylic additives combine with Ca2+, SiO42− and aluminate hydrate by cross-linking reaction. The cross-linking structure developed flocs which was embedded in calcium silicate hydrate (C–S–H) gel and intertwined around stirring shaft. The practicable methods were proposed to relieve or solve the abnormal phenomenon of cement slurry.

Modification of ultra-high-molecular-weight polyethylene fibers and powders using low-temperature plasma

Literature data on the surface modification of ultra-high-molecular-weight polyethylene as fibers and powder under the influence of low-temperature plasma are analyzed. The change in polymer chemical composition and structure is described. The results of the studies, indicating a significant improvement in the contact and adhesion characteristics of the modified polymer and composite materials, are discussed.

Changes in the structure of cell wall polymers in thermomechanical treatment of highly lignified plant feedstock

The effect of mechanical treatment at various temperatures on structural changes in polymers contained in highly lignified plant feedstock was studied by the example of reed stems. The optimal conditions (about 10°C) of mechanical activation of plant feedstock were determined, under which its structure is disordered enough for subsequent enzymatic hydrolysis, but the lignin decomposition is prevented, and so is the formation of a layer of substances inhibiting enzymes on the surface of particles.

Synthesis of allyl end‐block functionalized poly(ε‐caprolactone)s and their facile post‐functionalization via thiol–ene reaction

ABSTRACTA simple and facile strategy for the functionalization of commercial poly(ε‐caprolactone) diols (PCLs) with pendant functionalities at the polymer chain termini is described. Well‐defined allyl‐functionalized PCLs with varying numbers of allyl end‐block side‐groups were synthesized by cationic ring‐opening polymerization of allyl glycidyl ether using PCL diols as macroinitiators. Further functionalization of the allyl‐functionalized PCLs was realized via the UV‐initiated radical addition of a furan‐functionalized thiol to the pendant allyl functional groups, showing the suitability for post‐modification of the PCL materials. Changes in polymer structure as a result of varying the number of pendant functional units at the PCL chain termini were demonstrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 928–939

Low temperature plasma for textiles disinfection

The aim of the study was to evaluate the effectiveness of low temperature plasma (LTP) disinfection and its impact on cotton, linen, and silk. Research included: optimization of LTP parameters (time: 5, 10 min, gases: oxygen, nitrogen, argon and their mixtures); antimicrobial effectiveness of LTP for artificially aged and 19th-20th century textiles; impact of LTP on the mechanical, optical and structural (SEM, FTIR) textiles properties, and their susceptibility to colonization by microorganisms after LTP. The effectiveness of LTP disinfection was evaluated for the following microorganisms: Streptomyces sp., Bacillus megaterium, Pseudomonans fluorescens (silk), Aspergillus niger, Penicillium funiculosum and Trichoderma viride (cotton and linen). LTP for 10 min with oxygen provided the highest antimicrobial effect, and the number of microorganisms was reduced by 1–4-fold on the logarithmic scale (R = 69.64–99.99%), depending on the strain and textile. LTP increased textiles’ breaking strength. LTP did not caused significant changes in molecular structure of the fiber-forming polymers (cellulose and fibroin). In addition, it also lightened the colour and microdamaged the disinfected textiles. Nevertheless, LTP prevented microorganisms from colonizing the textiles for up to 21 days. Thus, this method can be a suitable alternative to currently used disinfection methods for textile, but should be used carefully for historical textiles.

Raman study of PANI thin film during long time period in dependence on storage conditions

Conducting polymer polyaniline which is nowadays in forefront of the interest was in our study prepared in a form of thin films from anilinium sulfate by its chemical oxidation using ammonium peroxydisulfate. During the oxidation process, the polyaniline was deposited on glass slides and immersed into reaction mixture. Two sets of polyaniline thin films were prepared with different oxidation times (10, 20, 30, and 40 min). The first set was kept dry in desiccator and the second one was freely exposed to air moisture. Raman spectroscopy, nondestructive technique which is very sensitive to changes in structure of polymers, was used for the characterization of the protonation state of prepared polyaniline thin films. It was found that storage conditions affect the protonation state which in case of samples kept in desiccator is maintained without significant changes for longer time. Raman spectroscopy also revealed the dependence of protonation state on the oxidation time and 10 min proved as not sufficient for the creation of the protonation form of polyaniline.

Mechanically activated enzymatic hydrolysis of yeast biomass

Experimental data obtained in studying processes that occur during the mechanoenzymatic hydrolysis of cell wall polymers of Saccharomyces cerevisiae yeast are presented. Special emphasis is placed on studying the reactivity of polymers contained in the supramolecular structure of cell walls, and on scaling the technology using pilot and industrial equipment. It is shown that mechanical treatment of yeast biomass allows us to alter the supramolecular structure of cell wall polymers and increase their reactivity in the enzymatic hydrolysis. Mechanical treatment disintegrates yeast cells and changes the supramolecular structure of polymers in their cell walls; the structural layers of a cell wall become disordered and diffused. A phenomenological model of mechanically activated enzymatic hydrolysis is proposed; the model is based on an autolocalization mechanism of the process. The domestic commercially available enzyme preparation CelloLux 2000 (OOO PA Sibbiopharm, Berdsk, Novosibirsk oblast) is used in this work. It is shown that changes in the supramolecular structure of yeast cell wall polymers occur during mechanically activated enzymatic hydrolysis. The yields of mannanoligosaccharides (1.1%) and mannanoproteins (2.7%) in the main extract are determined. Using pilot and industrial equipment at OOO PA Sibbiopharm, the technology is scaled and the production of a new mannanoligosaccharide product for animal husbandry is established. The pilot batch of the final product is effective against salmonellosis and is shown to increase the weight gain of experimental animals.

Real-time tracking of the hierarchical structure of biodegradable poly(butylene succinate-co-terephthalate) nanocomposites with fibrous attapulgite nanoparticles

Clearly understanding the structural development of materials during their preparation and processing allows for the fabrication of materials with expected properties that can be tailored for specific applications. In this work, we first presented the generation of poly(butylene succinate-co-terephthalate) (PBST) nanocomposites by combining the polymerization of copolymer with the simultaneous incorporation of fibrous attapulgite (ATP) nanoparticles with good dispersion. The lamellar structure, crystallization behavior and mechanical properties of PBST nanocomposites can be regulated by tuning the content of nanoparticles. The effects of nanoparticle morphology on the structure and properties of PBST nanocomposites with fibrous ATP and spherical silica nanoparticles also were investigated. The question why ATP nanoparticles always bring about faster crystallization rate and larger elongation at break than those caused by silica nanoparticles was answered as well. Furthermore, a schematic for the evolution of the hierarchical structure of PBST nanocomposites at each level during cooling was proposed. It was found that the formation and development of the hierarchical structure of PBST nanocomposites were highly temperature-dependent, and their cumulative growth leads to the final crystalline and hierarchical state. Studies of nanoparticles themselves and detailed changes of polymer structure in various scales are opening pathways for engineering flexible composites that can exploit the advantages of both polymers and nanoparticles.

Mechanistic Design of Polymer Nanocarriers to Spatiotemporally Control Gene Silencing.

Current siRNA delivery systems lack the ability to precisely tune siRNA release and maximize gene silencing in a spatiotemporal manner. Herein, we investigate photoresponsive block copolymer solution assemblies, for which stimuli-triggered changes in polymer structure altered nanocarrier stability and defined siRNA activity. Uniquely, our biomaterials design enabled the development and validation of a simple kinetic model that accurately predicted the extent of intracellular nanocarrier disassembly and silencing. Moreover, our constructs showed that maximal gene silencing could be achieved using concentrations of siRNA 5-fold lower than typical formulations due to the ability to rapidly release sufficient amounts of siRNA to saturate the cellular RISC machinery. The ability of our nanocarriers to remain dormant prior to phototriggered siRNA release allowed for the generation of cell patterns in gene expression with spatial control on cellular length scales and no detectable off-target effects. Furthermore, precisely tuned changes in nanocarrier structure enabled the modulation of protein and mRNA knockdown levels in murine fibroblasts and terminally differentiated human primary cells. These advances lead to increased precision, potency, and utility relative to other recent spatiotemporally controlled nucleic acid delivery vehicles reported in the literature. Moreover, the combination of experimental examination and kinetic modeling described herein should be applicable to a host of systems for which temporal control over nucleic acid delivery is a critical parameter in influencing cellular responses.

Environmental stress cracking in gamma-irradiated polycarbonate – A diffusion approach

Polycarbonate (PC) is an engineering polymer which presents interesting properties. This material has been also used in medical devices, which is frequently exposed to gamma radiosterilization and to chemical agents. This may produce significant changes in polymer structure, leading to failure in service. The present work brings about a new approach on environmental stress cracking (ESC) processes elucidation in 100kGy gamma-irradiated PC, by evaluating the diffusion process of methanol or 2-propanol in test specimens and determining the diffusion parameters on solvent-irradiated polymer systems. A comparison of diffusion parameters for both solvents indicated that methanol has a considerable ESC action on PC, with diffusion parameter of 7.5×10−14±1%m2s−1 for non-irradiated PC and 7.8×10−14±2.8%m2s−1 for PC irradiated at 100kGy. In contrast, 2-propanol did not act as an ESC agent, as it did promote neither swelling nor cracks in the test specimens. These results were confirmed by visual analysis and optical microscopy. Unexpectedly, structural damages evidenced in tensile strength tests suggested that 2-propanol is as aggressive as methanol chemical for PC. Moreover, although some manufacturers indicate the use of 2-propanol as a cleaning product for PC artifacts, such use should be avoided in parts under mechanical stress.

Radiation damage in polymer films from grazing‐incidence X‐ray scattering measurements

ABSTRACTGrazing‐incidence X‐ray scattering (GIXS) is widely used to analyze the crystallinity and nanoscale structure in thin polymer films. However, ionizing radiation will generate free radicals that initiate crosslinking and/or chain scission, and structural damage will impact the ordering kinetics, thermodynamics, and crystallinity in many polymers. We report a simple methodology to screen for beam damage that is based on lithographic principles: films are exposed to patterns of X‐ray radiation, and changes in polymer structure are revealed by immersing the film in a solvent that dissolves the shortest chains. The experiments are implemented with high throughput using the standard beam line instrumentation and a typical GIXS configuration. The extent of damage (at a fixed radiation dose) depends on a range of intrinsic material properties and experimental variables, including the polymer chemistry and molecular weight, exposure environment, film thickness, and angle of incidence. The solubility switch for common polymers is detected within 10–60 s at ambient temperature, and we verified that this first indication of damage corresponds with the onset of network formation in glassy polystyrene and a loss of crystallinity in polyalkylthiophenes. Therefore, grazing‐incidence X‐ray “patterning” offers an efficient approach to determine the appropriate data acquisition times for any GIXS experiment. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1074–1086

Temperature solidification preparations from polymeric composite materials at the microwave oven heating

The analysis of prospects of development space-rocket hardware technicians speaks about increase in a share of polymeric composite materials in designs of flying machines. But their manufacture is connected with certain expenses of energy. And it puts forward a problem of working out of new technologies of reception of products from polymeric composite materials on time reduction solidification polymeric binding without decrease in quality polymeric composite materials. Wide application space-rocket hardware technicians have found fibreglasses in products on a basis epoxy binding and fibrous filler (fabrics, fibres, plaits). For experimental working off of technological process solidification polymeric composite materials on samples the microwave, as a source of electromagnetic radiation of ultrahigh frequency has been chosen. Researches spent at different values of capacity on an exit of a microwave and heating time. Influence electromagnetic field the microwave oven on process solidification thermosetting polymers leads to creation of more sewed and more ordered structures that promotes increase of physicomechanical properties of a material. Studying of structural changes in polymers spent a method X-ray. In work supervised volume shrinkage hydrostatic weighing binding by a method. The received results have allowed to choose the optimal mode solidification binding under the influence of electromagnetic field the microwave oven whom the microwave oven to temperature 130°С in a current of 14 minutes with the subsequent free cooling in the furnace to temperature 60° and after that - consists in heating electromagnetic field at the open furnace - cooling to room temperature. This mode provides fuller solidification compositions (degree solidification - 97,5 %) after comparison with convection a method.

Polymeric Materials for Membrane Contactor Devices Applied to Water Treatment by Ozonation

In water treatment process ozone is applied to disinfection and to remove organic pollutants. Membrane contactor devices are used as a physical barrier to separate two fluids without phase dispersion and it can be used to improve the ozonation efficiency. Polymeric materials are used in membrane contactors and they can react with ozone, suffering degradation and losing its mechanical properties. In this work, commercial polymeric membranes were selected to investigate their interaction with ozone in gaseous phase. It was evaluated changes in polymer structures and in membrane morphology by FTIR, DSC, TGA and SEM. It was observed preferential ozone attack to double carbon-carbon bonds in the main polymer chain for polyimide and polysulphone membranes. Polypropylene has single carbon-carbon bonds and its reaction with ozone was less intensive. For polydimethylsiloxane membranes the ozone attack seems to occur in the carbon-silicon bond, leading to loss of mechanical and thermal properties.

Weathering of wood-polypropylene and wood-wollastonite-polypropylene composites containing pigments in Finnish climatic conditions

Purpose – The purpose of this paper is to study the resistance of wood-polypropylene and wood-wollastonite-polypropylene composites containing pigments to natural weathering. Design/methodology/approach – Natural weathering of composites was conducted in Finnish climatic conditions for one year. The colour of the composites was determined with a spectrophotometer, the morphology of the composite surface was analysed by scanning electron microscopy (SEM), and the changes in the polymer structure in surface layer of the composites were analysed with differential scanning calorimetry (DSC). Charpy impact strength was determined with an impact tester. Findings – The pigments used in this study reduced the colour change of the composites exposed to outdoor weathering as compared with the un-coloured composite. The carbon black pigment was more effective than the iron oxide pigment. Moreover, only the carbon black pigment was found to reduce the degradation of the surface layer of the composites. The addition of the carbon black pigment had a positive effect on the dimensional stability of the composites in a water absorption test. Only the combination of the carbon black pigment and wollastonite resulted in a composite which was capable to retain its Charpy impact strength both after one year of outdoor weathering and cyclic treatment. Research limitations/implications – This study is a part of continuous research on the development of wood-polymer composites (WPUs) suitable for outdoor applications in Finnish climatic conditions. The first part of the study, which has been published earlier, showed the results of weathering of composites in accelerated tests in comparison with 1,000 hours outdoor exposure during summer time (June and July). Outdoor weathering limited to 1,000 hours cannot give an objective view on the weathering behaviour of composites in Finnish climatic conditions. The results of the current study were obtained from one-year outdoor exposure of composites. Originality/value – The wood-polypropylene composite made with the combination of the carbon black pigment and wollastonite can be recommended for outdoor applications. The study provides useful information on the resistance of wood-polypropylene composites to weathering in Finnish climatic conditions.

Non-thermal plasma assisted polymer surface modification and synthesis: A review

This article reviews the applications of plasma to polymer surface modification and polymer synthesis. Plasma treatment causes changes in morphology, structure and properties of polymers. When polymers are treated using plasma, certain monomers with functional groups can be copolymerized with backbone chain or be loaded on the surface, which would help couple reaction of existing polymer chains, graft monomers onto polymers, immobilize proteins, carry antimicrobial drugs, and enhance cell attachment. Hence, non-thermal plasma process creates unique properties on polymers which allow improved and expanded applications of polymers in food packaging and biotechnology. Keywords: plasma, modification, synthesis, NTP, polymers, functional groups DOI: 10.3965/j.ijabe.20140702.001 Citation: Cheng Y L, Wang Y K, Chen P, Deng S B, Ruan R. Non-thermal plasma assisted polymer surface modification and synthesis: A review. Int J Agric & Biol Eng, 2014; 7(2): 1－9.

Influence of ageing on the gloss, color, and structure of colored ABS

AbstractThe results of examination of the influence of ageing by UV rays on the gloss, color, and morphology of injection molded parts made of ABS terpolymer with addition of coloring agents in the form of powder and its masterbatch (granulate) based on ABS and PS media are presented in this article. It has been shown that the UV radiation contributes to decrease in the value of gloss and increase in the luminance of moldings and also changes values of parameters a and b, describing the change in parts color, in the direction of red and yellow, which is connected with the degradation of polymer ABS and coloring agents. Ageing process leads to structural changes in polymer, depending on the type of coloring agent. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 392–398, 2016

Effects of Polymer Hydrophobicity on Protein Structure and Aggregation Kinetics in Crowded Milieu.

We examined the effects of water-soluble polymers of various degrees of hydrophobicity on the folding and aggregation of proteins. The polymers we chose were polyethylene glycol (PEG) and UCON (1:1 copolymer of ethylene glycol and propylene glycol). The presence of additional methyl groups in UCON makes it more hydrophobic than PEG. Our earlier analysis revealed that similarly sized PEG and UCON produced different changes in the solvent properties of water in their solutions and induced morphologically different α-synuclein aggregates [Ferreira, L. A., et al. (2015) Role of solvent properties of aqueous media in macromolecular crowding effects. J. Biomol. Struct. Dyn., in press]. To improve our understanding of molecular mechanisms defining behavior of proteins in a crowded environment, we tested the effects of these polymers on secondary and tertiary structure and aromatic residue solvent accessibility of 10 proteins [five folded proteins, two hybrid proteins; i.e., protein containing ordered and disordered domains, and three intrinsically disordered proteins (IDPs)] and on the aggregation kinetics of insulin and α-synuclein. We found that effects of both polymers on secondary and tertiary structures of folded and hybrid proteins were rather limited with slight unfolding observed in some cases. Solvent accessibility of aromatic residues was significantly increased for the majority of the studied proteins in the presence of UCON but not PEG. PEG also accelerated the aggregation of protein into amyloid fibrils, whereas UCON promoted aggregation to amyloid oligomers instead. These results indicate that even a relatively small change in polymer structure leads to a significant change in the effect of this polymer on protein folding and aggregation. This is an indication that protein folding and especially aggregation are highly sensitive to the presence of other macromolecules, and an excluded volume effect is insufficient to describe their effect.