Sets Of Copolymers Research Articles

Conferring fluorescence tracking function to polyphenylene sulfide by embedding the pyrene into the backbone at the molecular level: Design and synthesis

Morphological changes and damage degrees of PPS can be tracked and detected by fluorescence during service. However, the functionalization of the main chain of PPS is limited. To explore its luminescent properties for fluorescence tracking, 1,6-dibromopyrene and 1,3,6,8-tetrabromopyrene were employed to construct Dbp-PPS (Dibromopyrene-PPS) and Tbp-PPS (Tetrabromopyrene-PPS) with fluorescence tracking, respectively. These two sets of copolymers were systematically designed, synthesized, and characterized by Uv–Vis, PL, FT-IR, TGA, DSC, and XRD. To sum up, both Dbp-PPS and Tbp-PPS displayed visible fluorescence. UV–vis spectra showed an absorption maximum at λabs = 262–411 nm. PL spectra demonstrated emission maximum at λem = 450–545 nm. Particularly, 0.25%Dbp-PPS emitted the most intense blue fluorescence with the emission maximum at 450 nm and the absolute quantum yield of Φf = 0.08. The fluorescence decay lifetime of 0.25%Dbp-PPS comprised two components with lifetimes of 0.43 and 1.17 ns, implying the formation of excimer. The IR and XRD spectra of Dbp-PPS and Tbp-PPS were in line with those of PPS. TGA measurements illustrated that introducing pyrene into PPS is favorable for improving thermal stability. The DSC analysis indicated their melting temperature ranged from 260.9 to 280.4 °C and Dbp-PPS exhibited a little better melting point (279.4–280.4 °C) than neat-PPS (278.4 °C). Meanwhile, the resultant copolymers possessed a flexural strength of 31.0–101.5 MPa and tensile strength of 69.2–96.7 MPa. Both the flexural and tensile strengths of only 0.25%Dbp-PPS (101.5 and 86.8 Mpa) were higher than that of neat-PPS (95.1 and 84.3 Mpa). Imparting the pyrene unit into the PPS backbone is an effective method to give the PPS fluorescence tracking function for inspecting or tracking the polymer during their application and keep the original high performance of the PPS. Importantly, the systematic studies for pyrene-containing PPS in the current work provide a practical polymer tracking strategy suitable for other aromatic polymers such as poly (ether ether ketone), poly (ether sulfone).

Structure–Property Relationship in Poly(Terphenylene)-Based Anion Exchange Membranes; The Impact of Backbone Structure for the Free Volume Control in Alkaline Fuel Cell Application

The commercial application of anion exchange membrane fuel cells (AEMFCs) has been impeded by the lack of high ion conductivity and mechanical/chemical stability of the currently used anion exchange membranes (AEMs). A new class of aromatic polymers, which contain conducting head groups directly onto the polymer backbone were developed to attain long-term stability along with high conductivity. Inspired from this, a series of poly(terphenylene)-based anion exchange membranes devoid of benzylic sites or aryl-ether bonds, that are vulnerable to attack by hydroxide ion, were synthesized and were investigated for their physicochemical properties for alkaline fuel cell applications. The polymer backbones having N,N-dimethylpiperidinium conducting head group were synthesized using acid-catalyzed Friedel-Crafts polycondensation reaction between N-methyl-4-piperidone and meta/para-terphenyl monomers. Along with meta-terphenyl homopolymer, another three sets of copolymers were synthesized by introducing the kink structured meta-terphenyl in different ratios with para-terphenyl to control the free volume. The copolymer membrane, m-p-CoP-50, prepared from meta/para terphenyl monomers with a 1:1 molar ratio displayed a well-balanced water uptake, dimensional stability and the highest conductivity. The experimental procedures and the results will be discussed in detail.

Poly(2-oxazoline) glycopolymers with tunable LCST behavior

A series of thermo-responsive glyco-poly(2-oxazoline)s based on 2-ethyl-2-oxazoline and 2-(dec-9-enyl)-2-oxazoline were prepared. To study the effect of the sugar content on the solution behavior in water, two sets of copolymers with constant monomer-to-initiator ratios of 20 and 50 and varying amounts of the hydrophobic alkene functionalized monomer were synthesized. The glycopolymers were obtained by the photoaddition of 2,3,4,6-tetra-O-acetyl-1-thio-β-D-glycopyranose onto the double bonds followed by deacetylation of the saccharide residues. Turbidimetry measurements of the respective glycopolymers revealed a decreasing cloud point temperature with increasing amount of sugar moieties, proposed to be caused by hydrogen bonding between the sugars and the polymer amide groups, which is enabled by the flexibility of the long decyl spacer. Due to the linear relationship between cloud point temperatures and the sugar content, the cloud points can be easily tailored for specific applications.

Effect of Polymer Composition on Polymer Diffusion in Poly(butyl acrylate-co-methyl methacrylate) Latex Films

We describe polymer diffusion measurements in poly(butyl acrylate-co-methyl methacrylate) [P(BA−MMA)] copolymer latex films by fluorescence resonance energy transfer (FRET). Four sets of copolymers were prepared from various weight ratios of butyl acrylate and methyl methacrylate by semicontinuous emulsion polymerization. Their glass transition temperatures range from 4 to 28 °C. Latex particles were labeled with phenanthrene (Phe) as the donor dye and with 4-(N,N-dimethylamino)benzophenone (NBen) as the acceptor dye. Latex films were cast from a 1:1 mixture of Phe- and NBen-labeled latex samples. Polymer diffusion was monitored as a function of annealing temperature, and apparent diffusion coefficients (Dapp) were calculated from the energy transfer data using a simple diffusion model. These values increased with annealing temperature and decreased with Tg. Rheology measurements recorded the response of the dynamic moduli (G‘, G‘ ‘) with respect to oscillatory shear frequency (ω) over a range of temperature close to that of the diffusion experiments. The temperature dependence of polymer dynamics extracted by the rheology experiments is in good agreement with the temperature dependence of Dapp. Increasing the BA copolymer content leads to an apparent increase in long-chain branching, which is reflected in both the time dependence of Dapp and in the dynamic moduli measurements. A greater degree of branching leads to a broader distribution of polymer diffusion coefficients and a stronger time dependence of Dapp.

Functionalized polymer networks: synthesis of microporous polymers by frontal polymerization

A series of glycidyl methacrylate (GMA)-ethylene dimethacrylate (EGDM) copolymers of varying compositions were synthesized by free-radically triggered thermal frontal polymerization (FP) as well as by suspension polymerization (SP) using azobisisobutyronitrile [AIBN] as initiator. The two sets of copolymers were characterized by IR spectroscopy and mercury intrusion porosimetry, for determination of epoxy number and specific surface area. Frontal polymerization was more efficient, yielding greater conversions at much shorter reaction times. The self-propagating frontal polymerization also generates microporous material with narrow pore size distribution. It yields higher internal pore volume and surface area than suspension polymerization, surface morphologies are, however, inferior.

Aggregation behavior of acrylamide/2-phenoxyethyl acrylate and its interaction with sodium dodecyl sulfate in aqueous solution studied by proton 1D and 2D NMR

H-1 NMR self-diffusion coefficient, spin-lattice relaxation time, spin-spin relaxation time, and two-dimensional nuclear Overhauser enhancement (2D NOESY) measurements have been used to study the association behavior of a novel hydrophobically associating copolymer composed of acrylamide ( AM) and a small amount of 2-phenoxyethyl acrylate ( POEA), and its interaction with the anionic surfactant sodium dodecyl sulfate (SDS). Three sets of copolymers with approximately the same composition but with different hydrophobic POEA contents were investigated. The POEA contents for these copolymers were about 1.41, 1.03, and 0.56 mol% respectively, as validated by H-1 NMR spectra. Self-diffusion coefficient measurements show that the aggregation process occurs in a relative narrow concentration range and the critical association concentrations (cacs), of these copolymers are within this narrow concentration range, which are in agreement with those measured by viscosity measurements (6 g L-1). Above this concentration, the hydrophobic POEA moieties are found to associate and possibly build a transitory three-dimensional network along the polyacrylamide (PAM) backbones, which induces a strong decrease in NMR parameters including self-diffusion coefficients and relaxation times. The surfactant SDS showed a significant interaction with the copolymer in the dilute solution. Addition of SDS resulted in the binding of SDS on copolymer POEA-PAM segments and reinforced the interchain transient network formation of copolymer at a concentration below its cac. In the SDS/POEA-PAM mixed systems, the hydrophobic methylene groups of the SDS molecules were preferentially located in the vicinity of the phenoxy groups of the POEA hydrophobes.

Frontal copolymerization of 2‐hydroxyethyl methacrylate and ethylene glycol dimethacrylate without porogen: comparison with suspension polymerization

AbstractNetworked, crosslinked poly[(2‐hydroxyethyl methacrylate)‐co‐(ethylene glycol dimethacrylate)] (HEMA‐EGDM) was synthesized by frontal polymerization (FP) using azobisisobutyronitrile as initiator. HEMA‐EGDM copolymers of similar composition were also synthesized by suspension polymerization. The two sets of copolymers were characterized for functional groups (IR), pore volume (mercury intrusion porosimetry), surface area (nitrogen adsorption) and morphology (scanning electron microscopy). FP‐generated polymeric network structures had higher internal pore volumes and surface areas but their surface morphologies were inferior to those of copolymers synthesized by suspension polymerization. Copyright © 2004 Society of Chemical Industry

Copolymers of poly( n-alkyl acrylates): synthesis, characterization, and monomer reactivity ratios

Poly( n-alkyl acrylate) copolymer reactivity ratios were determined for n-alkyl acrylate monomers of various side-chain lengths n ranging from 6 to 22. Two sets of copolymers were synthesized to less than <10% conversion to evaluate the reactivity ratios. The first set included P(A10- co-A14), P(A10- co-A18), and P(A14- co-A18); while the second set consisted of P(A6- co-A12), P(A6- co-A22) and P(A12- co-A22). Copolymers were formed from monomer mixtures at 25 mol% intervals ranging from 0 through 100 mol%. 13C NMR was performed on the homo polymers and the low conversion copolymers to determine the reactivity ratios of the monomers in each copolymer system. It was determined that the reactivity ratios for all monomers examined here were approximately equal to one. Physical properties of the copolymers, including melting point, heat of fusion, and permeation as a function of temperature, of the low conversion polymers were compared to copolymers formed at 100% conversion to demonstrate that these properties are independent of conversion because no composition drift occurs during polymerization.

Porous thiiranyl polymers: Newer supports for immobilization of penicillin G acylase

Spherical and macroreticular epithiopropyl methacrylate-ethylene glycol dimethacrylate (thiiranyl) and glycidyl methacrylate-ethylene glycol dimethacrylate (glycidyl) copolymer beads of two differing copolymer compositions were synthesized. Particle size was estimated to be in the range 250–420 μm for both sets of copolymers. The anomalous increase in both surface area and pore volume with crosslinking density reflects a bimodal distribution of the internal porous structure in both these copolymers. These reactive copolymer beads were investigated for the binding and expression of a biocatalyst, penicillin G acylase. The activity of immobilized penicillin G acylase obtained, 191 IU/g, compares well with established industrial immobilized enzymes.

Porous copolymers of trimethylolpropane triacrylate and acrylonitrile

AbstractThe homopolymer of trimethylolpropane triacrylate (TMPA) was synthesized by suspension polymerization using a thermodynamically good solvent (toluene) as a porogen (vol. ratio 1:1). This polymer possesses a high specific surface area (437 m2 · g−1) and porosity (50%). It was found by sorption of benzene and cyclohexane that the majority of the pores are in the range of 1–5 nm. Sorption of phenol, a standard sorbate, from a water solution is proportional to the specific surface area of the mesopores. This sorption is higher than that of nonspecific sorbents (like styrene/divinylbenzene copolymers) and smaller than the sorption of specific ones (like acrylonitrile/divinylbenzene copolymers).Two sets of reactive copolymers were obtained. In the first set, TMPA (20–40 vol.‐%) was polymerized with acrylonitrile (AN) in the presence of a constant amount of toluene as an inert diluent (vol. ratio 1:1). In the second set of copolymers the cross‐linking degree was kept constant (30 or 40 vol.‐% of TMPA) but various solvent mixtures were used, namely: toluene/tetradecane or hexadecane, toluene/2‐ethylhexanol, cyclohexanol/tetradecane or hexadecane, cyclohexanol/2‐ethylhexanol (vol. ratio 9:1). It was found that all the copolymers are macroporous (volume of pores approx. 1,0 cm3 · g−1) but those obtained in the presence of good solvents display a higher specific surface area and hence better sorption properties towards phenol than those obtained in the presence of poor solvents. The swelling of AN/TMPA copolymers is smaller than that of the TMPA homopolymer due to the presence of additional physical crosslinks formed by the strongly polar nitrile groups.

Copolymerisation radicalaire du méthacrylate de méthyle et du chlorure de vinylidène avec ou sans dérive de composition

AbstractTwo sets of methylmethacrylate‐vinylidene chloride copolymers were prepared via radical copolymerization in dimethylformamide. The first set is carried out in batches. Gas‐chromatographic analysis of samples allows a kinetic study from which the reactivity ratios rM ‐ 2.73 and rC ‐ 0.24 are derived. For the second set a new apparatus, briefly described, has been used. It permits to keep constant the composition of the monomer mixture, through addition of methyl methacrylate, monitored by a chromatographic analysis. The two sets of copolymers are analyzed using nuclear magnetic resonance (60 MHz) leading to the triad distribution, from which the reactivity ratios are derived. Owing to the composition drift, the method cannot be applied to the first set of copolymers; but in that case, it is possible to calculate the triad distribution, the knowledge of the reactivity ratios, and the calculation fits quite well the experimental results.