Different Classes Of Polymers Research Articles

Mass Spectrometry Insight for Assessing the Destiny of Plastics in Seawater

Plastic pollution has become an increasingly serious environmental issue that requires using reliable analytical tools to unravel the transformations of primary plastics exposed to the marine environment. Here, we evaluated the performance of the isotope ratio mass spectrometry (IRMS) technique for identifying the origin of polymer material contaminating seawater and monitoring the compositional alterations due to its chemical degradation. Of twenty-six plastic specimens available as consumer products or collected from the Mediterranean Sea, five plastics were shown to originate from biobased polymeric materials. Natural abundance carbon and hydrogen isotope measurements revealed that biopolymers incline to substantial chemical transformation upon a prolonged exposure to seawater and sunlight irradiation. To assess the seawater-mediated aging that leads to the release of micro/nano fragments from plastic products, we propose to use microfiltration. Using this non-destructive separation technique as a front end to IRMS, the fragmentation of plastics (at the level of up to 0.5% of the total mass for plant-derived polymers) was recorded after a 3-month exposure and the rate and extent of disintegration were found to be substantially different for the different classes of polymers. Another potential impact of plastics on the environment is that toxic metals are adsorbed on their surface from the seashore water. We addressed this issue by using inductively coupled mass spectrometry after nitric acid leaching and found that several metals occur in the range of 0.1-90 µg per g on naturally aged plastics and accumulate at even higher levels (up to 10 mg g-1) on pristine plastics laboratory-aged in contaminated seawater. This study measured the degradation degree of different polymer types in seawater, filling in the gaps in our knowledge about plastic pollution and providing a useful methodology and important reference data for future research.

Aromatic polyamide nonporous membranes for gas separation application

Abstract Polymer membrane-based gas separation is a superior economical and energy-efficient separation technique over other conventional separation methods. Over the years, different classes of polymers are investigated for their membrane-based applications. The need to search for new polymers for membrane-based applications has been a continuous research challenge. Aromatic polyamides (PAs), a type of high-performance materials, are known for their high thermal and mechanical stability and excellent film-forming ability. However, their insolubility and processing difficulty impede their growth in membrane-based applications. In this review, we will focus on the PAs that are investigated for membrane-based gas separations applications. We will also address the polymer design principal and its effects on the polymer solubility and its gas separation properties. Accordingly, some of the aromatic PAs developed in the authors’ laboratory that showed significant improvement in the gas separation efficiency and placed them in the 2008 Robeson upper bound are also included in this review. This review will serve as a guide to the future design of PA membranes for gas separations.

Relationship between water permeability and physical characteristics of polyolefins, vinyl polymers, and polycarbonates

Diagrams of compatibility of water permeability with glass transition temperature, density, and cohesion energy are constructed. The computer program “Cascade”, INEOS RAS was used. Polyolefins, vinyl polymers, and polycarbonates were analyzed. Compatibility diagrams are constructed for the areas of lowest and highest water permeability for different classes of polymers. For polyolefins and vinyl polymers, the lowest water permeability is selected in the range from 0 to 100 barrer, and the highest water permeability is from 1000 to 2000 barrer. For polycarbonates, the intervals from 0 to 70 barrer and from 3000 to 7000 barrer are selected. These diagrams allow you to select polymers that meet the specified values of density, cohesion energy, glass transition temperature, and the onset of temperature of intense thermal degradation.

Mechanically interlocked 3D multi-material micromachines

Metals and polymers are dissimilar materials in terms of their physicochemical properties, but complementary in terms of functionality. As a result, metal-organic structures can introduce a wealth of novel applications in small-scale robotics. However, current fabrication techniques are unable to process three-dimensional metallic and polymeric components. Here, we show that hybrid microstructures can be interlocked by combining 3D lithography, mold casting, and electrodeposition. Our method can be used to achieve complex multi-material microdevices with unprecedented resolution and topological complexity. We show that metallic components can be combined with structures made of different classes of polymers. Properties of both metals and polymers can be exploited in parallel, resulting in structures with high magnetic responsiveness, elevated drug loading capacity, on-demand shape transformation, and elastic behavior. We showcase the advantages of our approach by demonstrating new microrobotic locomotion modes and controlled agglomeration of swarms.

Optical Analysis of the Internal Void Structure in Polymer Membranes for Gas Separation.

Global warming by greenhouse gas emissions is one of the main threats of our modern society, and efficient CO2 capture processes are needed to solve this problem. Membrane separation processes have been identified among the most promising technologies for CO2 capture, and these require the development of highly efficient membrane materials which, in turn, requires detailed understanding of their operation mechanism. In the last decades, molecular modeling studies have become an extremely powerful tool to understand and anticipate the gas transport properties of polymeric membranes. This work presents a study on the correlation of the structural features of different membrane materials, analyzed by means of molecular dynamics simulation, and their gas diffusivity/selectivity. We propose a simplified method to determine the void size distribution via an automatic image recognition tool, along with a consolidated Connolly probe sensing of space, without the need of demanding computational procedures. Based on a picture of the void shape and width, automatic image recognition tests the dimensions of the void elements, reducing them to ellipses. Comparison of the minor axis of the obtained ellipses with the diameters of the gases yields a qualitative estimation of non-accessible paths in the geometrical arrangement of polymeric chains. A second tool, the Connolly probe sensing of space, gives more details on the complexity of voids. The combination of the two proposed tools can be used for a qualitative and rapid screening of material models and for an estimation of the trend in their diffusivity selectivity. The main differences in the structural features of three different classes of polymers are investigated in this work (glassy polymers, superglassy perfluoropolymers and high free volume polymers of intrinsic microporosity), and the results show how the proposed computationally less demanding analysis can be linked with their selectivities.

Entry pressure correlations in capillary flow

The entry pressure in capillary rheometry is determined by using the Bagley correction method to accurately determine the viscosity of polymers at high shear rates. This method requires the use of at least three capillary dies having the same diameter and different lengths. In this paper, the entry pressure of over 40 sets of experimental data for different polymers is correlated as a function of wall shear stress for two different classes of polymers, namely, linear and branched. The derived correlations can directly be applied to correct the raw capillary data from a single capillary die, thus minimizing the experimental error, effort, and time.

Melt Electrowriting of Thermoplastic Elastomers.

Melt electrowriting (MEW), an additive manufacturing process, is established using polycaprolactone as the benchmark material. In this study, a thermoplastic elastomer, namely, poly(urea-siloxane), is synthesized and characterized to identify how different classes of polymers are compatible with MEW. This polyaddition polymer has reversible hydrogen bonding from the melt upon heating/cooling and highly resolved structures are achieved by MEW. The influence of applied voltage, temperature, and feeding pressure on printing outcomes behavior is optimized. Balancing these parameters, highly uniform and smooth-surfaced fibers with diameters ranging from 10 to 20 µm result. The quality of the 3D MEW scaffolds is excellent, with very accurate fiber stacking capacity-up to 50 layers with minimal defects and good fiber fusion between the layers. There is also minimal fiber sagging between the crossover points, which is a characteristic of thicker MEW scaffolds previously reported with other polymers. In summary, poly(urea-siloxane) demonstrates outstanding compatibility with the MEW process and represents a class of polymer-thermoplastic elastomers-that are, until now, untested with this approach.

Structure-Property Relationships in CO2-philic (Co)polymers: Phase Behavior, Self-Assembly, and Stabilization of Water/CO2 Emulsions.

This Review provides comprehensive guidelines for the design of CO2-philic copolymers through an exhaustive and precise coverage of factors governing the solubility of different classes of polymers. Starting from computational calculations describing the interactions of CO2 with various functionalities, we describe the phase behavior in sc-CO2 of the main families of polymers reported in literature. The self-assembly of amphiphilic copolymers of controlled architecture in supercritical carbon dioxide and their use as stabilizers for water/carbon dioxide emulsions then are covered. The relationships between the structure of such materials and their behavior in solutions and at interfaces are systematically underlined throughout these sections.

Improved performance of a reactive polymer-based bituminous mixes – effect of cross-linking agent

Polymer-modified bitumen (PMB) is being practiced today worldwide as pavement performance boosters for ensuring its long life under extreme conditions of load, climate, traffic density, etc. Various national and international specs on the subject recommend a series of polymer chemistries for this application, but elastomeric polymers such as styrene–butadiene–styrene (SBS) are preferred due to their certain inherent advantages. However, universally a need is felt to allow the use of different classes of polymers, to enable producers of PMBs to cut cost through wider availability of polymers. Our research studies focused on preparing a PMB formulation, based on a reactive polymer, belonging to trans-polyoctenamer group. This research study showed that the PMB produced in the lab, by blending a reactive polyoctenamer polymer along with a trace amount of sulphur as a cross-linking agent, gives excellent performance almost equivalent to SBS-based PMB. There was a noticeable improvement in the elastic recovery properties.

A comparative study on the effects of Co-60 gamma radiation on polypropylene and polyimide

Polypropylene (PP) and polyimide (PI), which belong to entirely different classes of polymers, are irradiated by Co-60 gamma radiation under similar doses and similar conditions in the dose range varying from 57.6 to 230.4 kGy. The radiation responses of these two polymers are analyzed by various characterizations such as Fourier transform infrared, UV–visible, energy-dispersive spectroscopy, X-ray diffraction, scanning electron microscopy and contact angle. PP shows substantial modifications in its structure and properties while in the same dose range, PI shows remarkable stability. These two different responses are interpreted in terms of physicochemical structure and properties of these polymers.

Noble gases as indicators of molecular-selective gas transport in polymeric membranes

Methods of estimation of molecular-selective gas transport parameters in polymeric membranes and explanation of separation selectivity evolution for ‘small’ and ‘large’ molecules up to inversed selectivity are proposed based on comparative analysis of diffusion and solubility of noble gases as isotropic diffusion probes in different classes of polymers and block copolymers on their basis. Two approaches are considered in this work: (1) analysis of diffusional migration of permanent gases, lower hydrocarbons, and alcohols (vapor) in glassy polymers and rubbers relative to the diffusion of noble gases including radon; (2) adaptation of the ‘hard sphere’ theory developed for gas solubility in liquids to the calculation of the solubility of gases in the polymer matrix. In the latter case, noble gases as isotropic probes are used for calculating the required fitting parameters of the polymer medium.

Influence of residual solvent on physical and chemical properties of amorphous glassy polymer films

One of the most important areas of current research is the study of the influence of the prehistory of samples of amorphous glassypolymersontheirphysicalandchemicalproperties.ThestudyofstructuralchangesbyhightemperatureIRspectroscopy compared with of quantum chemical calculations allows for an understanding of the mechanism and nature of such processes. The changes in the structure of the polymer chain depending on the type of solvent used in the formation of the films are demonstrated using the examples of several different classes of polymers. In turn, the impact of such changes in the structure on the physical and chemical properties of the polymer films is demonstrated. c � 2013 Society of Chemical Industry

Evaluation of the Structural Determinants of Polymeric Precipitation Inhibitors Using Solvent Shift Methods and Principle Component Analysis

The presence of polymers within solid dose forms, such as solid dispersions, or liquid or semisolid formulations, such as lipid-based formulations, can promote the maintenance of drug supersaturation after dissolution or dispersion/digestion of the vehicle in the gastrointestinal tract. Transiently stable supersaturation delays precipitation, increases thermodynamic activity, and may enhance bioavailability and reduce variability in exposure. In the current study a diverse range of 42 different classes of polymers, with a total of 78 polymers across all classes, grades, and molecular weights were examined, to varying degrees, as potential polymeric precipitation inhibitors (PPIs) using a solvent shift method to initiate supersaturation. To provide a deeper understanding of the molecular determinants of polymer utility the data were also analyzed, along with a range of physicochemical descriptors of the polymers employed, using principle component analysis (PCA). Polymers were selectively tested for their ability to stabilize supersaturation for nine poorly water-soluble model drugs, representing a range of nonelectrolytes, weak acids, and weak bases. In general, the cellulose-based polymers (and in particular hydroxypropylmethyl cellulose, HPMC, and its derivatives) provided robust precipitation inhibition across most of the drugs tested. Subsequent PCA indicate that there is consistent PPI behavior of a given polymer for a given drug type, with clear clustering of the performance of polymers with each of the nonelectrolytes, weak bases, and weak acids. However, there are some exceptions to this, with some specific drug type-polymer interactions also occurring. Polymers containing primary amine functional groups should be avoided as they are prone to enhancing precipitation rates. An inverse relationship was also documented for the number of amide, carboxylic acid, and hydroxyl functional groups; therefore for general good PPI performance the number of these contained within the polymer should be minimized. Molecular weight is a poor predictor of performance, having only a minor influence, and in some cases a higher molecular weight enhances the precipitation process. The importance of ionic interactions to the ability of a PPI to stabilize the supersaturated state was demonstrated by the advantage of choosing a polymer with an opposite charge with respect to the drug. Additionally, when the polymer charge is the same as the supersaturated drug, precipitation is likely to be enhanced. A PCA model based on polymer molecular properties is presented, which has a central oval region where the polymer will general perform well across all three drug types. If the polymer is located outside of this region, then they either show compound-specific inhibition or enhance precipitation. Incomplete separation of the PPI performance based on the molecular properties on the polymers indicates that there are some further molecular properties that might improve the correlation.

Development and evaluation of chitosan based oral controlled matrix tablets of losartan potassium

Aim and Background:The novelty of the present study was to control the release profile of matrix tablets of losartan potassium prepared by using different concentrations of chitosan and trisodium citrate as cross-linking agent with combination of various release retardant polymers.Materials and Methods:Twelve formulations were prepared using HPMC K100M, carbopol 934P, and xanthan gum as polymers. Matrix tablets were prepared by wet granulation technique. The granules were subjected to precompression parameters such as angle of repose, loose bulk density, tapped bulk density, compressibility index. Tablets were evaluated for weight variation, hardness, drug content, in-vitro dissolution, stability studies, respectively. Drug -polymer compatibility studies were determined by FTIR spectroscopy. Further stability studies were carried out for 3months in accelerated conditions at 40°C and 75%RH. The granules of all formulations exhibited good flow and compressibility. In-vitro dissolution studies were carried out for 24 h using 0.1 N HCl for the first 2 h and pH 6.8 phosphate buffers for the remaining 22h.Results:It was found that among the 12 formulations F11 and F12 showed good dissolution profile to control the drug release. The release data was fitted to various mathematical models such as, Higuchi, Korsmeyer, first-order, and zero-order to evaluate the kinetics and the drug release. The drug release follows zero-order kinetics and the mechanism was found to be diffusion controlled and Case II transport. FT-IR spectroscopic studies revealed no interaction between drug and polymer. The stability studies indicated that F11 and F12 formulations were stable for 3months.Conclusion:The above results concluded that by combining different classes of polymers an acceptable release profile can be obtained in the fluctuating in vivo environment.

Discrimination of Polymers by Using Their Characteristic Collision Energy in Tandem Mass Spectrometry

The characteristic collision energy to obtain 50% fragmentation, expressed as the characteristic collision voltage (CCV), was used as a tool to discriminate different classes of polymers. The CCV value of different polymers was determined in a quadrupole ion trap mass spectrometer. Good linear correlation (0.980 < R(2) < 0.999) between the CCV values and precursor ion mass was found for all polymers studied. The position of the various linear trend lines varied among the various polymers, which allowed their grouping based on the respective CCV values. The collision energy necessary to drive fragmentation was decreasing in the order of polyethers > polymethacrylates > polyesters > polysaccharides. This suggests that polysaccharides fragment most easily (low CCVs), while polyethers require the highest collision energy among the polymers studied. The effect of end group on the CCV was also studied, showing a minor influence in most cases. In addition, the applicability of CCV as discriminator was studied for a mixture of (1) polylactic acid (PLA), (2) poly(tetramethylene glycol) (PTMEG), and (3) PLA-block-PTMEG-block-PLA block copolymer. Differences between the CCV values of four nominally isobaric polymers (of which two were copolymers and two were homopolymers) were observed. These results demonstrate that the insertion of a "weak" link into a polymer chain significantly affects the energy required for fragmentation.

Nonaqueous Emulsions – A Versatile Tool for New Types of Functional Nanoparticles

AbstractSummary: The preparation of functional polymer latex particles is usually carried out in aqueous heterogeneous systems, i.e. for example in emulsion or mini‐emulsion polymerization. Due to the presence of water, moisture sensitive reactions like step growth polymerizations or metal catalyzed reactions can not be accomplished without side reactions and / or decomposition. In order to avoid these side reactions, different nonaqueous emulsion systems have been developed. According to the desired polymerization procedure, these systems consist of a nonpolar organic phase surrounded by a perfluorinated solvent or of a polar organic phase which is dispersed in a nonpolar organic solvent. Both emulsions are stabilized by amphipolar block copolymers and result in long time stable particle dispersions. The resulting dispersions yield particles with narrow size distributions and – depending on the reaction conditions – diameters down to tens of nanometers. This technique allows the formation of particles consisting of numerous different classes of polymers, e.g. polyurethanes, polyesters, polyolefins etc. and the formation of more complex morphologies such as core shell structures.

Vapor‐induced swelling of supported methacrylic and siloxane polymer films: Determination of interaction parameters

AbstractWhite light reflectance spectroscopy is applied to monitor vapor‐induced thickness changes of polymer films, supported on suitable silicon substrates. Assuming unidirectional swelling due to the constraining support, the equilibrium volume swelling of four methacrylic polymers and two siloxane‐based copolymers upon exposure to various activities of water, methanol, ethanol, and ethyl acetate vapor, at 30°C is evaluated. The deduced sorption isotherms were fitted to the Flory‐Huggins equation and interaction parameters, as well as solubility coefficients at infinite solute dilution, were deduced for each binary system. The relative sorption capacity of the different classes of polymers toward the four vapors are in line with the expected solubility interactions between solvent and solute. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Analytical mass spectrometry of poly(ethylene glycol) additives in artists’ acrylic emulsion media, artists’ paints, and microsamples from acrylic paintings using MALDI–MS and nanospray-ESI–MS

Poly(ethylene glycol) (PEG) compounds in artists’ acrylic emulsion paint products from different paint manufacturers, ranging from base emulsions (Rohm and Haas, Röhm and Scott Bader), to modified emulsions and complete paints (Rowney, Winsor and Newton, Golden, Liquitex, Lascaux), were characterised with a newly developed mass spectrometric method which combines data from Matrix assisted laser desorption/ionisation mass spectrometry (MALDI–MS) and nano-electrospray ionisation mass spectrometry (nano-ESI–MS(MS)). MALDI–MS was used for the determination of the molar mass distribution (MMD) and calculation of the molar mass averages ( M w and M n), the polydispersity index ( D) and the relative amount of a specific distribution if multiple PEGs were present. Electrospray ionisation mass spectrometry was used for the end-group analysis. Three different classes of polymers was found being PEG, polypropylene glycol (PPG) and a block copolymer of polyethylene glycol/polypropylene glycol (PEG/PPG) with molar mass averages ranging from 400 to 4200 Da. PEG compounds with a nonylphenyl or an octylphenyl hydrophobic end-group are most common. The hydrophilic end-groups observed are hydroxide and/or sulphate. Water extracts of microsamples from a palette by David Hockney dating from 1970 and samples paintings by Patrick Caulfield (1936–2005) and John Hoyland (born in 1934) were investigated with the same technique. Although some artist paint manufacturers use the same specific base emulsions to make their paints, the composition of the PEG compounds present in the water extracts of the palette and paintings samples made it possible, in some cases, to suggest a specific brand of paint used by the artist.

Self-assembled and etched cones on laser ablated polymer surfaces

At least two different routes lead to conical structures on laser ablated polymer surfaces. These were investigated by studying laser ablation on the surfaces of different classes of polymers. Cones appeared readily in strongly absorbing polymers such as poly(ethylene terephthalate) (PET) and polyimide (PI), but only within narrow laser parameters in nylon 6, and rarely in poly(chlorotrifluoroethylene), the last two being weak ultraviolet (UV) absorbers. Self-assembled, close-packed cones occurred in PET, in which heat generated due to absorbed laser energy creates a thin, chemically stable, viscoelastic, highly compliant layer (above the glass transition temperature). Surface structure in such polymers evolves from nodules through donuts into ripples and finally to cones as the energy deposited per unit area on the surface (total fluence) is increased using a combination of single pulse fluence and number of pulses. A phase transition from a ripple phase to a cone phase is thought to occur as the thickness of the viscoelastic surface layer increases above a critical value. Cones began to appear from almost the beginning of the irradiation process at random locations in PI, a polymer whose surface irreversibly turns into a hard solid upon exposure to either or both UV and heat. It is proposed that the radiation hardened spots serve as nuclei, a cone “grows” out of this as the material surrounding this nuclei is ablated. The initial sparse occurrence of cones in PI-like polymers, and the increase in their number density with total fluence until the surface is densely packed with cones can be explained by a nucleation and growth model.

Water Vapor Sorption Mechanism and Hygroscopicity of Textile Materials

It is shown that the quasichemical model bears much more information on the supramolecular structure of polymers and the mechanism of sorption of water vapor than the equations borrowed from the theory of adsorption on "rigid" adsorbents. The physical meaning of the constants and limitations of the existing equations formally used for describing sorption in swollen systems are analyzed. The constants of the quasichemical model for sorption of water vapor by different classes of polymers are reported.