Gel Permeation Chromatography Data Research Articles

Effect of Molecular Weight and Chemical Structure of Terminal Groups on the Properties of Porous Hollow Fiber Polysulfone Membranes

For the first time, polysulfones (PSFs) were synthesized with chlorine and hydroxyl terminal groups and studied for the task of producing porous hollow fiber membranes. The synthesis was carried out in dimethylacetamide (DMAc) at various excesses of 2,2-bis(4-hydroxyphenyl)propane (Bisphenol A) and 4,4'-dichlorodiphenylsulfone, as well as at an equimolar ratio of monomers in various aprotic solvents. The synthesized polymers were studied by nuclear magnetic resonance (NMR), differential scanning calorimetry, gel permeation chromatography (GPC), and the coagulation values of 2 wt.% PSF polymer solutions in N-methyl-2-pyrollidone were determined. According to GPC data, PSFs were obtained in a wide range of molecular weights Mw from 22 to 128 kg/mol. NMR analysis confirmed the presence of terminal groups of a certain type in accordance with the use of the corresponding monomer excess in the synthesis process. Based on the obtained results on the dynamic viscosity of dope solutions, promising samples of the synthesized PSF were selected to produce porous hollow fiber membranes. The selected polymers had predominantly -OH terminal groups and their molecular weight was in the range of 55-79 kg/mol. It was found that porous hollow fiber membrane from PSF with Mw 65 kg/mol (synthesized in DMAc with an excess of Bisphenol A 1%) has a high helium permeability of 45 m3/m2∙h∙bar and selectivity α (He/N2) = 2.3. This membrane is a good candidate to be used as a porous support for thin-film composite hollow fiber membrane fabrication.

Glycosaminoglycans from the Starfish Lethasterias fusca: Structures and Influence on Hematopoiesis.

Crude anionic polysaccharides extracted from the Pacific starfish Lethasterias fusca were purified by anion-exchange chromatography. The main fraction LF, having MW 14.5 kDa and dispersity 1.28 (data of gel-permeation chromatography), was solvolytically desulfated and giving rise to preparation LF-deS with a structure of dermatan core [→3)-β-d-GalNAc-(1→4)-α-l-IdoA-(1→]n, which was identified according to NMR spectroscopy data. Analysis of the NMR spectra of the parent fraction LF led to identification of the main component as dermatan sulfate LF-Derm →3)-β-d-GalNAc4R-(1→4)-α-l-IdoA2R3S-(1→ (where R was SO3 or H), bearing sulfate groups at O-3 or both at O-2 and O-3 of α-l-iduronic acid, as well as at O-4 of some N-acetyl-d-galactosamine residues. The minor signals in NMR spectra of LF were assigned as resonances of heparinoid LF-Hep composed of the fragments →4)-α-d-GlcNS3S6S-(1→4)-α-l-IdoA2S3S-(1→. The 3-O-sulfated and 2,3-di-O-sulfated iduronic acid residues are very unusual for natural glycosaminoglycans, and further studies are needed to elucidate their possible specific influence on the biological activity of the corresponding polysaccharides. To confirm the presence of these units in LF-Derm and LF-Hep, a series of variously sulfated model 3-aminopropyl iduronosides were synthesized and their NMR spectra were compared with those of the polysaccharides. Preparations LF and LF-deS were studied as stimulators of hematopoiesis in vitro. Surprisingly, it was found that both preparations were active in these tests, and hence, the high level of sulfation is not necessary for hematopoiesis stimulation in this particular case.

Temperature Dependence of the Kinetic Parameters of the Titanium–Magnesium Catalyzed Propylene Polymerization

This paper provides a study of the liquid-phase polypropylene polymerization on a heterogeneous titanium-magnesium Ziegler-Natta-type catalyst. A kinetic model was developed that included the activation of potential active centers, chain growth, transferring the chains to hydrogen and monomer, and the deactivation of active centers. The model was created to predict the polymerization rate, polymer yield, and average molecular weights of polymer chains where the polymerization temperature changes from 40 to 90 °C. In developing polycentric kinetic models, there is a difficulty associated with evaluating the kinetic constants of the rates of elementary reactions/stages in polymerization. Each heterogeneous titanium-magnesium catalyst (TMC), including a co-catalyst, as well as an internal and an external electron donor, has its own set of kinetic parameters. Therefore, its kinetic parameters must be defined for each new catalyst. The presented algorithm for identifying the kinetic constants of rates starts with a kinetic model that considers one type of active centers. At the second stage, a deconvolutional analysis is used for the molecular weight distribution (MWD) of the gel permeation chromatography (GPC) data of the polypropylene samples and the most probable distribution of Flory chain lengths is found for each type of active centers. At the third stage, the single-center model is transformed into a polycentric kinetic model. For the catalyst system, five types of active centers were identified, together with a mass fraction and a number-average molecular weight for each active center type of the catalyst, which is consistent with the published results for similar Ti-based Ziegler-Natta catalysts.

Thermoresponsive oligo(ethylene glycol) methyl ether methacrylate homopolymers via RAFT polymerization in 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids

Responsive polymer-based materials vary their physicochemical properties upon external stimuli. In the past decades, these materials have been utilized in diverse applications such as drug delivery, tissue engineering, biosensors, and surface coatings. In these applications, stimuli-responsive polymers with narrow dispersity are ideal to ensure good sensitivity. RAFT polymerization remains one of the living polymerization techniques that affords great control over polymer size and dispersity. Herein, we investigated how the solvent size, RAFT agent choice, and monomer size affect the RAFT polymerization of thermoresponsive OEGMEMA in hexafluorophosphate-based RTILs. Gel permeation chromatography (GPC) results showed that increased RTIL chain length resulted in an increased polymerization rate, polymer size and dispersity. The RAFT agent CPDB provided better control over the polymerization kinetics. Moreover, GPC data revealed an inverse relationship between the monomer size and the dispersity of its polymer. Monomer size also restricted polymer growth with decreasing rate through time. Among the homopolymers, P(DEGMEMA) synthesized in [HMIM]PF6 and CPBD exhibited the highest percent conversion, fastest reaction rate, and relatively high size uniformity. Our findings demonstrate that a thermoresponsive P(DEGMEMA) can be rapidly obtained in high molecular weights and conversion in RTILs.

Epoxidation of Tall Oil Fatty Acids and Tall Oil Fatty Acids Methyl Esters Using the SpinChem® Rotating Bed Reactor

Tall oil fatty acids are a second-generation bio-based feedstock finding application in the synthesis of polyurethane materials. The study reported tall oil fatty acids and their methyl esters epoxidation in a rotating packed bed reactor. The chemical structure of the synthesized epoxidized tall oil fatty acids and epoxidized tall oil fatty acids methyl ester were studied by Fourier-transform infrared spectroscopy. Average molecular weight and dispersity were determined from gel permeation chromatography data. The feasibility of multiple uses of the Amberlite® IRC120 H ion exchange resin as a catalyst was investigated. Gel permeation chromatography chromatograms of epoxidized tall oil fatty acids clearly demonstrated the formation of oligomers during the epoxidation reaction. The results showed that methylation of tall oil fatty acids allows obtaining an epoxidized product with higher relative conversion to oxirane and much smaller viscosity than neat tall oil fatty acids. Epoxidation in a rotating packed bed reactor simplified the process of separating the catalyst from the reaction mixture. The Amberlite® IRC120 H catalyst exhibited good stability in the tall oil fatty acids epoxidation reaction.Graphical

Nanoindentation for Fast Investigation of PET Film Degradation

The lifetime of industrial polymer products is in many cases limited by aging. Therefore, it is necessary to develop a fast and sensitive method to detect polymer aging at an early stage. A commercially available 50-µm-thick and transparent polyethylene terephtalate (PET) film was aged under different artificial conditions, and the evolution of mechanical properties with increasing aging time was investigated via nanoindentation (NI) and tensile testing. Chemical aging was studied with gel permeation chromatography (GPC), and physical aging was monitored by the first heating of differential scanning calorimetry. NI data evaluated with the method of Oliver and Pharr was compared to tensile test data with good agreement between the results on the macro- and nanoscales. Furthermore, a correlation between NI creep data and GPC data was obtained, which indicates that the aging of the PET films primarily originated from chemical aging. This study states that NI is an appropriate method to determine degradation of PET at an early stage.

Single-step synthesis and energy-efficient coloration of wool textiles with poly(amino naphthalene sulfonic acid)-based dyes by oxidation polymerization

In the context of sustainability, energy-efficient low-temperature dyeing with non-toxic polymeric dyes is attractive. In this work, a single-step method of simultaneous synthesis of polymeric dyes from non-toxic amino-naphthalene sulfonic acids (ANSAs) by the oxidation polymerization and energy-efficient coloration of wool fabric was developed. The studied monomers are 7-amino-1,3-naphthalene monopotassium disulfonate (ANSA-1), 4-amino-1-naphthalene sulfonic acid (ANSA-2), and 5-amino-2-naphthalene sulfonic acid (ANSA-3). The prepared polymeric dyes were characterized by UV–vis, Fourier transform infrared (FT-IR), and mass spectrometry, and gel permeation chromatography (GPC). The mass spectra suggest that oxidation treatment of ANSA-1 formed only dimers but the other two ANSAs formed polymers, whereas the GPC data demonstrated successful polymerization of all three ANSAs. The treated fabrics were characterized by thermogravimetric analysis, and FTIR and reflectance spectroscopies. The treatment parameters, including the monomer and oxidant concentrations, treatment pH, temperature, and time, affected the shade of the color produced and its intensity. The optimum conditions for dyeing with ANSAs were 50 °C, 120 min, and a 1:1 monomer to oxidant ratio. The treatment with these ANSAs produced various colors in the fabric including tonal changes. The colorfastness to washing increased with an increase in the treatment temperature and time. The shade of color produced and the color intensity were dependent on the position of the substituent sulfonate groups in the amino-naphthalene compounds. This developed treatment can be used for the energy-efficient dyeing of wool and other polyamide fibers with good colorfastness to washing.

Molecular weight characteristics of polyetheretherketone (PEEK): analysis of determination conditions

Polyetheretherketone (PEEK), which is highly resistant to aggressive media and various types of radiation, is widely used in various industries. At the same time, the information on the molecular weight characteristics of PEEK, which is necessary for the creation of polymer materials with specifi ed properties, is quite limited. Determination of these characteristics is complicated by the almost complete insolubility of PEEK in organic solvents. The work is devoted to the analysis of the applicability of viscometry, determination of the melt fl ow index and gel permeation chromatography (GPC) for assessing the molecular weight characteristics of PEEK. The preliminary modifi cation of the polymer to transform it into a soluble state has been considered as an alternative approach. A GPC-method of the determination of molecular mass of sulfonated PEEK has been developed. The values of average molecular weights for samples produced by Petrov Institute of Plastics and a commercial sample Victrex 150G were determined. Good agreement of the GPC data with the results of determining the melt fl ow index of the polymer makes it possible to consider the latter as an express method for assessing the molecular weight of a polymer.

Structure and functionality of cassava starch in different deep eutectic solvents/water mixtures: A comparative study

Starch, as one of the most abundant natural polysaccharides, is regarded as a sustainable material due to its renewability, biodegradability, and modifiability, and is widely used as an excellent industrial material. However, as a polyhydroxyl polymer, native starch has low solubility in most situations due to its network structure formed by intramolecular and intermolecular hydrogen bonds, which limits its industrial application. In this study, the solubility of cassava starch (CS) in a series of acidic, neutral, and alkaline deep eutectic solvents (DESs) was investigated. Relatively high solubilities of 52.8 wt%, 11.4 wt%, and 10.2 wt% were obtained in choline chloride/formic acid (CF), ethylammonium chloride/ethylene glycol (EE), and choline chloride/diethanolamine (CD), respectively. The dissolution behavior of CS in pure mixtures of these DESs and in DESs/water mixtures (2:8) was also compared. The results of gel permeation chromatography (GPC) analysis showed that the weight-average molecular weights (Mw) and number-average molecular weights (Mn) were ranked in the order CF > EE > CD. The same pattern was observed for the DESs/water mixtures (2:8), although the reduction in Mw and Mn was less distinct than in the pure DESs. The results of X-ray diffraction, small-angle X-ray scattering, and scanning electron microscope observations were consistent with the GPC data, i.e., the hydrolysis ability of CS was higher in the acidic DESs (CF) compared to the neutral (EE) and alkaline (CD) DESs. The dissolution behaviors of CS in the DESs/water mixtures were affected by the structure of the DESs and their water content. These results demonstrate that aqueous DESs serve as excellent media for starch dissolution. Moreover, this study provides a comprehensive understanding of the solubilization behavior of CS in different aqueous DESs and provides insights into the development of novel starch-based materials using DESs.

One-Pot Preparation of Metal-Polymer Nanocomposites in Irradiated Aqueous Solutions of 1-Vinyl-1,2,4-triazole and Silver Ions.

Metal–polymer nanocomposite polyvinyltriazole–silver nanoparticles were obtained using one-pot synthesis in irradiated aqueous solutions of 1-vinyl-1,2,4-triazole (VT) and silver ions. Gel permeation chromatography data show that upon radiation initiation, the molecular weight of poly(1-vinyl-1,2,4-triazole) increases with increasing monomer concentration. To study the kinetics of polymerization and the features of the radiation–chemical formation of nanoparticles, UV-Vis spectroscopy was used. TEM images show a relatively small average size of the forming nanoparticles (2–3 nm) and a narrow size distribution, which shows the effective stabilization of nanoparticles by triazole substituents at a molar ratio of VT and silver ions of 25/1. The addition of ethyl alcohol was used to increase the efficiency of synthesis and suppress the crosslinking of macromolecules in solution. The results of the work show that aqueous–alcoholic solutions of 1 wt.% VT can be used to obtain soluble nanocomposite materials. 10 wt.% monomer solutions have prospects for use in the preparation of polymer gels filled with nanoparticles.

Antileishmanial activity evaluation of poly(thymolformaldehyde)—A biobased material from thymol

A new biobased compound was prepared from commercially available monoterpene thymol, obtained from the essential oil of a cultivated plant, Thymus vulgaris L. (Lamiaceae), together with formaldehyde. The final product, poly(thymolformaldehyde), namely PTF, was characterized by infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), UV–vis spectroscopy, fluorescence, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and differential scattering calorimetry (DSC). NMR associated with FTIR data analysis evidenced the occurrence of polymerization at C-1 and C-5 positions of thymol. UV–vis and fluorescence analysis showed that the prepared material exhibited absorption and emission bands at 285 and 313 nm, respectively. GPC data analysis displayed a polydisperse material (PDI = 1.99) with a molar mass of approximately 1375 Da, while TGA analysis showed a high thermal resistance (ranging from 150 to 800 °C). PTF was evaluated against promastigote forms of Leishmania (Leishmania) amazonensis and exhibited effective concentration 50 % (EC50) of 8.4 ± 0.8 μg/mL as well as reduced toxicity to macrophages (cytotoxic concentration 50 % - CC50 > 100 μg/mL and SI > 11.9). Therefore, the effects of PTF against L. (L.) amazonensis, together with its simple preparation using commercially available reagents (thymol and formaldehyde), suggest that this polymer could be a promising candidate for new biobased drugs to treat cutaneous leishmaniasis.

Comparative hydrolysis analysis of cellulose samples and aspects of its application in conservation science

Knowledge about the carbohydrate composition of pulp and paper samples is essential for their characterization, further processing, and understanding the properties. In this study, we compare sulfuric acid hydrolysis and acidic methanolysis, followed by GC–MS analysis of the corresponding products, by means of 42 cellulose and polysaccharide samples. Results are discussed and compared to solid-state NMR (crystallinity) and gel permeation chromatography (weight-averaged molecular mass) data. The use of the hydrolysis methods in the context of cellulose conservation science is evaluated, using e-beam treated and artificially aged cellulose samples.

Synthesis optimization, DFT and physicochemical study of chitosan sulfates

Chitosan is an important biologically active amino polysaccharide. Water-soluble sulfated chitosan derivatives are widely used as anticoagulant and antiviral drugs. In this study, new methods for sulfamic acid sulfation of chitosan in the presence of urea in 1,4-dioxane and in a deep eutectic solvent representing a mixture of sulfamic acid and urea have been proposed. Mathematical models of sulfation of chitosan in these systems have been built. The obtained sulfated chitosan derivatives have been investigated by Fourier-transform infrared spectroscopy, X-ray diffractometry, atomic force microscopy, gel permeation chromatography, elemental analysis, and the density functional theory. The introduction of the sulfate group into the chitosan molecule was proven by infrared spectroscopy. When using the sulfamic acid/urea mixture, side reactions of carbamation of chitosan have been observed. It has been established from the atomic force microscopy data that the sulfated chitosan film surface consists of spherical particles partially agglomerated with each other. According to the gel permeation chromatography data, sulfated chitosan obtained in different systems, but under the same conditions (temperature and time), has different molecular weight distributions. The molecular weight distribution curve of the sulfated chitosan obtained in the sulfamic acid‒urea‒1,4-dioxane system is significantly shifted to the high-molecular region (Mw ~ 36.6 kDa), while the sulfated chitosan obtained in the sulfamic acid/urea deep eutectic solvent (Mw ~ 27.2 kDa). The density functional theory calculation of chitosan sulfates in the B3LYP/6-31G(d, p) basis set have been made.

Synthesis of Poly(styrene sulfonyl chloride) via reversible addition-fragmentation chain transfer polymerization and characterization thereof for membrane applications

Reversible addition-fragmentation chain transfer (RAFT) polymerization has been examined for the synthesis of poly (styrene sulfonyl chloride) (PSSC) of high molecular weight and narrow polydispersity index (PDI). PSSC, contains reactive sulfonyl chloride that can allow use of organic solvent for membrane casting, and chemical modification through reactive sulfonyl groups. For PSSC preparation, end-capped styrene i.e. styrene sulfonyl chloride (SSC) is used as a monomer, which is derived from sodium 4-vinylbenzenesulfonate by chlorination with thionyl chloride. Fourier transform infrared spectroscopy, Raman spectroscopy and Proton nuclear magnetic resonance spectroscopy, have been successfully used to confirm the polymer architecture. End-group of PSSC containing RAFT agent (Cyanomethyl N-methyl-N-phenylcarbamodithioate), is also confirmed by fragmentation analysis using Gas chromatography-mass spectroscopy. Evaluation of PSSC by X-ray diffraction and differential scanning calorimetry showed that resulting polymer is predominantly amorphous in nature and has a glass transition temperature of 119 ​°C. Gel permeation chromatography data reveals formation of high molecular weight (84 ​kDa) PSSC with and low PDI (1.4). Moreover, PSSC can be converted to polyelectrolyte and can be crosslinked by interfacial polymerization concept; hence, it would have considerable prospective for membrane preparation for fuel cell and water purification.

Alternative Tanning Agent for Leather Industry from a Sustainable Source

Dialdehyde starches with different aldehyde content from native corn starch were prepared by sodium periodate oxidation to be used as a tanning agent in leather making. For this purpose, native corn starch was oxidized with sodium metaperiodate in different molar ratios. After oxidation processes, the yields, solubility in water and aldehyde contents of the obtained dialdehyde starches were determined as well as structure characterizations by Proton Nuclear Magnetic Resonance Spectroscopy, Fourier Transform Infrared Spectroscopy and Gel Permeation Chromatography. Evaluating the gel permeation chromatography data, the dialdehyde starch samples which were thought to be in appropriate molecular weight/size to penetrate into skin fibers were selected to be used in the tanning process. Their tanning abilities were evaluated by investigating hydrothermal stabilities, filling and fiber isolation characteristics and physical properties determined by mechanical tests and organoleptically. From the evaluation of the results, it was revealed that sodium metaperiodate oxidized starches which have appropriate molecular weight and adequate aldehyde content has a remarkable tanning effect and can be utilized as a tanning agent with the advantages of not necessitating pickling process which means saving time and simplifying the production but more importantly offering an important advantage from an environmental point of view.

High efficient recovery of L-lactide with lignin-based filler by thermal degradation

The biorefinery and high-value utilization are the development tendency in the study of lignin. Lignin-graft-poly(D-lactic acid) (LG-g-PDLA) is a new kind of poly(L-lactide) (PLLA) filler. In order to clarify the effects of LG-g-PDLA on PLLA pyrolysis, PLLA/LG-g-PDLA (1 wt% filler) and pure PLLA were prepared and subjected to reveal the degradation mechanisms with proton and carbon-13 nuclear magnetic resonance spectrometer (H- and 13C-NMR) and gel permeation chromatography (GPC). More L-LA and less D- and meso-lactide (D- and meso-LA) were recovered from PLLA/LG-g-PDLA at 240 °C. By analyzing the NMR and GPC data, the thermal degradation of PLLA/LG-g-PDLA was put forward as being possible mechanisms of less random and more unzipping depolymerization. The results of lactides yields at different conditions better guide the optimization of PLLA recovery. Moreover, this innovative blending approach can simultaneously achieve high-value utilization of lignin and recovery efficiency of PLLA.

Electrochemical Aminoxyl-Mediated Oxidation of Primary Alcohols in Lignin to Carboxylic Acids: Polymer Modification and Depolymerization.

An electrochemical process has been developed for chemoselective oxidation of primary alcohols in lignin to the corresponding carboxylic acids. The electrochemical oxidation reactions proceed under mildly basic conditions and employ 2,2,6,6-tetramethyl-1-piperidine N-oxyl (TEMPO) and 4-acetamido-TEMPO (ACT) as catalytic mediators. Lignin model compounds and related alcohols are used to conduct structure-reactivity studies that provide insights into the origin of the reaction selectivity. The method is applied to the oxidation of lignin extracted from poplar wood chips via a mild acidolysis method, and the reaction affords a novel polyelectrolyte material. Gel permeation chromatography data for the oxidized lignin shows that this material has a molecular weight and molecular weight distribution very similar to that of the extracted lignin, but notable differences are also evident. Base titration reveals a significant increase in the acid content, and the oxidized lignin has much higher water solubility relative to the extracted lignin. Treatment of the oxidized lignin under acidic conditions results in depolymerization of the material into characterized aromatic monomers in nearly 30 wt% yield.

Determination of modified polyamide 6's foaming windows by bubble growth simulations based on rheological measurements

ABSTRACTReactive extrusion was used to modify virgin polyamides 6 (v‐PA6) and to prepare chain extended PA6 (CE‐PA6) and long‐chain branched PA6 (LCB‐PA6) for the melt foaming process. This was done using a twin‐screw extruder and the following modifiers: a chain extender ADR‐4368 and a branching agent maleic anhydride grafted polypropylene. A reaction mechanism was proposed to explain the chain extension and long‐chain branching reactions and was verified by the Fourier transform infrared spectroscopy data. The analysis of the gel permeation chromatography data showed that LCB‐PA6 presented a strong increase in the molecular weight and in the dispersity index. Moreover, the rheological properties of the v‐PA6 and modified PA6 resins were characterized by a dynamic shear test. The LCB‐PA6 compared with CE‐PA6 showed much higher shear viscosity and longer characteristic relaxation times, indicating the presence of an LCB structure. A uniaxial elongation test showed that the LCB‐PA6 had the highest melt viscosity and melt strength as well as most obvious strain‐hardening behavior. A high‐pressure differential scanning calorimeter under compressed CO2 was used to investigate the PA6's crystallization properties so as to analyze its minimum temperature of foaming windows. The melt foamability of the CE‐PA6 and the LCB‐PA6 was verified by batch melt foaming experiments with CO2 as the blowing agent and maximum temperature of foaming windows was also quantitatively determined by numerical simulation of bubble growth based on the rheological measurements. The results showed that the LCB‐PA6 foams had a smaller cell diameter, a larger cell density, a greater expansion ratio, and wider foaming temperature window than the CE‐PA6. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48138.

Preparation and characterization of bio- and UV- degradable superabsorbent hydrogels based on a novel cross-linker

ABSTRACTWe prepared bio- and UV-degradable superabsorbent hydrogels based on a novel cross-linker. Fourier transform infrared, thermogravimetric (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and gel permeation chromatography (GPC) were employed to study the properties of the hydrogels. TG, DSC, and XRD data show that our hydrogels are amorphous polymer materials with excellent thermal stability. And they own high absorbency for water and aqueous solutions. Additionally, our superabsorbent hydrogels have good biodegradability and excellent UV degradability according to the GPC data. We suppose the superabsorbent hydrogels have potential applications in many important fields like hygienic products and agriculture due to their high absorbency for aqueous media and good bio- and UV degradability.

Process–Structure–Property Relationships for Porous Membranes Formed by Polymerization of Solid Monomer by a Vapor-Phase Initiator

We determine the mechanism that governs polymerization during a process in which solid monomer is polymerized with a vapor-phase initiator. Gel permeation chromatography data show a bimodal molecular weight distribution at all processing conditions which can be attributed to two different polymerization mechanisms. Smaller chains form by polymerization at the vapor–solid interface, and larger chains form by polymerization within the solid. The monomer mobility and sublimation rate affect the polymerization rate and thereby affect the membrane structure. The molecular weight of the larger chains can be increased by increasing the polymerization temperature and the polymerization time. The ability to vary the polymerization time allows for tuning the solubility of the membranes. The process–structure–property relationships elucidated in this study can enable the fabrication of porous polymer membranes for applications in filtration, textiles, and sensors.