Set Of Copolymers Research Articles

Synthesis and Properties of Thermotropic Copolyesters Based on Poly(ethylene terephthalate) and 4'-Acetoxy-4-biphenyl-carboxylic Acid.

A series of novel copolyesters based on polyethylene terephthalate (PET) and 4′-hydroxy-biphenyl-4-carboxylic acid (HBCA) was obtained by melt polycondensation of bis(2-hydroxyethyl) terephthalate and 4′-acetoxybiphenyl-4-carboxylic acid (ABCA) as co-monomers with Sb2O3 as a catalyst. Using this synthetic procedure, a set of copolymers containing 20–80 mol% of HBCA units was prepared. According to NMR spectroscopy, the copolymers were of random composition. Copolyesters comprising 60–80 mol% of HBCA possessed increased heat resistance and formed nematic melts at 270 °C and higher. The liquid crystal (LC) phase formation was accompanied by transition to non-Newtonian characteristics of the melt flow, as well as an equalization of storage and loss moduli values. According to XRD and polarizing microscopy, the LC glassy phase of the copolyesters coexists with crystalline regions of poly-(4′-hydroxy-4-biphenylcarboxylate), non-melting up to 400 °C and above. The mechanical characteristics of these LC copolyesters showed similar or better values than those of well-known LC polymers. These novel copolyesters can be useful in obtaining heat-resistant materials with an ordered structure and, as a consequence, improved performance.

Amphiphilic Dicyclopentenyl/Carboxybetaine-Containing Copolymers for Marine Fouling-Release Applications.

Zwitterionic materials received great attention in recent studies due to their high antifouling potential, though their application in practical coatings is still challenging. Amphiphilic polymers have been proven to be an effective method to combat fouling in the marine environment. This study reports the incorporation of small amounts of zwitterionic carboxybetaine methacrylate (CBMA) into hydrophobic ethylene glycol dicyclopentenyl ether acrylate (DCPEA). A new set of copolymers with varying amphiphilicities was synthesized and coated on chemically modified glass substrates. The antifouling capabilities were assessed against the diatom Navicula perminuta and multiple species in the field. Unsurprisingly, high diatom densities were observed on the hydrophobic control coatings. The integration of small zwitterionic contents of only ∼5 wt % was already sufficient to rapidly form a hydrophilic interface that led to a strong reduction of fouling. Ultralow fouling was also observed for the pure zwitterionic coatings in laboratory experiments, but it failed when tested in the real ocean environment. We noticed that the ability to absorb large amounts of water and the diffuse nature of the interphase correlate with the adsorption of silt, which can mask the hydrophilic chemistries and facilitate the settlement of organisms. The amphiphilic coatings showed low fouling in dynamic short-term field exposures, which could be explained by the reduced tendency of the coatings for sediment adsorption.

The effect of dendritic pendants on the folding of amphiphilic copolymers via supramolecular interactions

ABSTRACTThe supramolecular folding of amphiphilic heterograft copolymers equipped with dendritic pendants is investigated using a combination of proton nuclear magnetic resonance (1H NMR) spectroscopy, small‐angle X‐ray scattering, and circular dichroism spectroscopy. Hereto, the linear poly(ethylene glycol) pendants normally used to convey water compatibility are partially substituted with branched analogues. For one set of copolymers, second‐generation polyglycerol dendrons are directly attached to the polymer backbone, while for the other a hydrophilic linker is placed in between. The results show that the branching of the hydrophilic pendants affects the local structure of the folded copolymer but does not influence the overall conformation and single‐chain character of the folded copolymers in solution. All copolymers fold into 4–5 nm single‐chain polymeric nanoparticles with a very compact spherical morphology, independent of the dendritic content of the copolymer. Intriguingly, the incorporation of the dendritic pendants affects the formation of a structured interior even at low incorporation ratios. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 411–421

Synthesis of Degradable Poly[(Ethylene Glycol)-co-(Glycolic Acid)] via the Post-Polymerization Oxyfunctionalization of Poly(Ethylene Glycol).

To enhance the limited degradability of poly(ethylene glycol) (PEG), a straightforward method of synthesizing poly[(ethylene glycol)-co-(glycolic acid)] (P(EG-co-GA)) via a ruthenium-catalyzed, post-polymerization oxyfunctionalization of various PEGs is developed. Using this method, a set of copolymers with GA compositions of up to 8 mol% are prepared with minimal reduction in molecular weight (<10%) when compared to their commercially available starting materials. The P(EG-co-GA) copolymers are shown to undergo hydrolysis under mild conditions.

Functionalized Nanofiber Meshes Enhance Immunosorbent Assays.

Three-dimensional substrates with high surface-to-volume ratios and subsequently large protein binding capacities are of interest for advanced immunosorbent assays utilizing integrated microfluidics and nanosensing elements. A library of bioactive and antifouling electrospun nanofiber substrates, which are composed of high-molecular-weight poly(oxanorbornene) derivatives, is described. Specifically, a set of copolymers are synthesized from three 7-oxanorbornene monomers to create a set of water insoluble copolymers with both biotin (bioactive) and triethylene glycol (TEG) (antifouling) functionality. Porous three-dimensional nanofiber meshes are electrospun from these copolymers with the ability to specifically bind streptavidin while minimizing the nonspecific binding of other proteins. Fluorescently labeled streptavidin is used to quantify the streptavidin binding capacity of each mesh type through confocal microscopy. A simplified enzyme-linked immunosorbent assay (ELISA) is presented to assess the protein binding capabilities and detection limits of these nanofiber meshes under both static conditions (26 h) and flow conditions (1 h) for a model target protein (i.e., mouse IgG) using a horseradish peroxidase (HRP) colorimetric assay. Bioactive and antifouling nanofiber meshes outperform traditional streptavidin-coated polystyrene plates under flow, validating their use in future advanced immunosorbent assays and their compatibility with microfluidic-based biosensors.

Vapor-phase testing of the memory-effects in benzene- and toluene-imprinted polymers conditioned at elevated temperature

The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene and acetonitrile. The obtained materials were applied as coatings onto nickel–titanium (Ni–Ti) alloy wires which were incorporated into solid-phase microextraction devices and finally tested for their ability to competitively adsorb vapors from the headspace of an aqueous solution containing a few volatile organic compounds.Porosity analysis showed that, regardless of the solvent used, only a high cross-linking level permitted the preparation of mesoporous copolymers (BJH radius typically in the range 13–15nm), a requirement for providing accessibility to the targeted nanoscale-imprinted cavities. A noticeable exception was, however, observed for the MMA/DVB copolymers which exhibited much diminished BJH radius. The porosity data correlated well with the extraction profiles found, which suggested the presence of benzene-imprinted sites in all the highly cross-linked copolymers prepared in benzene, except for the MMA/DVB copolymers. Concerning the effect of an elevated conditioning temperature on the memory-effects created by the imprinting process, the results were clearly indicative that the tested copolymers, including the more robust highly cross-linked ones, are not suitable for high temperature applications such as solid-phase microextraction coupled to gas chromatography.

Molecular Weight Effect on the Quaternization of Poly(4-vinylpyridine) with Alkylbromide

The objective of this work is to study the influence of molecular weight on the quaternization of poly(4-vinylpyridine) (P4VP) with octyl and dodecyl bromide. The P4VP with different molecular weight was synthesized by radical polymerization. The molecular weight was determined by viscosimetric and light scattering. A set of copolymers containing the poly(4-vinylpyridine) of different molecular weights quaternized with octyl and dodecyl bromide (C8Br and C12Br) were prepared. In order to determine the solubility limit of each copolymer; phase diagrams were established according to the water percentage in the mixture water-ethanol. Empiric laws for the rate maximum (Tmax) and Mw were proposed. We have considered six P4VP samples in wide intervals of molecular weights: 0.75.104 to 94.104 g/mol. The ratio between the high size and the small size is 106.7. The maxima rate of quaternization (Tmax) and the initial constants rate k0 increase with P4VP molecular weights. Critical time for the quaternization kinetics is 360 h, which is independent of Mw. The length of alkyl chain from C8 does not affect the quaternization kinetics. The solubility of copolymers in water decreases with macromolecular weight,which is not the case for P4VP homopolymer.

Nanoparticles Made of Microbial Poly(γ-glutamate)s for Encapsulation and Delivery of Drugs and Proteins

This study focused on the preparation and evaluation of nanoparticles made of alkyl esters of microbial poly(γ-glutamic acid) (PGGA) to be used as drugs and proteins carrier and delivery systems. Racemic PGGA of bacterial origin was fully methylated or partially esterified to render non-water-soluble polymers. A set of co-polymers containing poly(glutamic acid) and ethyl, hexyl, dodecyl and octadecyl glutamate units with alkyl contents of 50 and 75% was prepared. Spherical nanoparticles with a diameter of 200–250 nm and a narrow distribution were generated from the alkylated polymers by the precipitation-dialysis method. These nanoparticles readily degraded hydrolytically upon incubation in simulated physiological medium at a rate dependent on the alkylation degree and the length of the alkyl group. All these nanoparticles were able to encapsulate efficiently erythromycin. Those made of carboxyl containing polyglutamates were also effective to load α-chymotrypsin. The release of such compounds from nanoparticles upon incubation proceeded essentially following the same profile that is followed in the hydrolysis of the corresponding substrate polymers. The loss of enzyme activity of the incubated protein diminished significantly upon encapsulation in these systems.

Copolymers based on fluorene dyads mixed to 3,4-ethylenedioxythiophene units: Optical properties of random versus regular structures

We report on the synthesis of two copolymers containing both ethylenedioxyhiophene (EDOT) derivatives and dihexylfluorene (DHF) units. In one hand, a set of copolymers was obtained by dehalogenating Yamamoto coupling from a feed solution of both monomers. This route leads to materials with a random composition of each monomer. The substitution by a tetradecyloxy chains on the dioxyethylene ring ensures a good solubility of the copolymer when increasing the proportion of the EDOT units in the structure. On the other hand, the second polymer was synthesized by Suzuki cross-coupling, the resulting structure being a fully alternated of one EDOT and two DHF. All polymers were characterised by steric exclusion chromatography, indicating in all cases that small polymeric chains are obtained. FT-IR and 1H NMR spectroscopy were investigated in order to solve the structure and to determine the EDOT/fluorene ratio of the random materials. The electronic and optical properties were investigated by UV–vis spectroscopy and Photoluminescence experiments. The role of EDOT units on the electronic structure of the copolymers has been established; mainly the electron-rich EDOT ring increases the HOMO energetic level. This observation is confirmed by cyclic voltamperometry experiments. This trend is also observed within a regular polymeric sequence. While the optical properties are finely controlled in this case, the photoluminescent properties are drastically hindered by the π-stacking that results from the highly ordered material during the cast process. These results confirm our choice to built electroluminescent devices with the random copolymers as active layers. Green light emission is obtained with moderate emission.

Thermoreactive displacers for anion exchange and hydroxyapatite displacement chromatography

A set of copolymers was prepared via radical copolymerization of N, N-dimethylacrylamide and 7-hydroxy-3-methyl-4-vinylindanone. While poly(N,N-dimethylacrylamide) is water-soluble at all temperatures, the copolymers showed a lower critical solution temperature (LCST), which depended on the composition. Independent of this LCST all copolymers can be used in the dissolved state as protein displacers in combination with anion exchange stationary phases. The indanone group of the polymers is known the chelate calcium ions. It was therefore also possible to use the polymers to displace acidic (i.e., C-site interacting) proteins from hydroxyapatite. The major advantage of the described displacers over existing agents stems from the fact that they can be almost quantitatively recovered by thermoprecipitation from the carrier but also from any given protein zone. Lowering of the temperature renders the polymers again fully soluble and ready for use. No unspecific protein coprecipitation was observed under these conditions within our analytical means.

A new way of improving non-linear optical properties of side-chain non-linear optically active copolymers

A new set of side-chain non-linear optical copolymers containing two different amounts of 2-methyl-4-nitroaniline (MNA) and disperse red 1 (DR1) chromophores are reported. From this set of copolymers, it is easy to see how to optimize such key properties as glass transition temperature, maximum absorption wavelength and second harmonic signal, d 33. The composition dependence of these properties is seen to vary linearly with MNA and DR1 content.

Co-crystallization in PEEK Copolymers

Thermal and wide-angle x-ray scattering (wAxs) studies of a new set of copolymers of polyether ether ketone (PEEK) with ether diphenyl ether ketone (EDEK) have been undertaken. The copolymerization modifies the properties of PEEK. At low levels of comonomer content the incorporation of the comonomer unit lowers the melting temperature and reduces the degree of crystallinity. At higher levels the melting point increases towards that of the PEDEK homopolymer. The x-ray structure is very similar to that of PEEK, consistent with rejection of the comonomer at low levels of comonomer content. At high levels the structure is very similar to that of PEDEK while at intermediate levels the structure is found to 'swtich' from that of PEEK to that of PEDEK, consistent with co-crystallization of the two monomer units.

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.

Influence of synthesis conditions of porous copolymers of 1,4‐di(methacryloyloxymethyl)‐naphthalene with divinylbenzene on their structure, 2. Influence of diluent composition

AbstractThe influence of diluent composition on the internal structure of porous copolymers of 1,4‐di(methacryloyloxymethyl)naphthalene (1,4‐DMN) and divinylbenzene (DVB) was studied.A set of copolymers containing 0.5 mole fraction of 1,4‐DMN and 0.5 mole fraction of DVB obtained in the presence of various amounts of toluene in the mixture with n‐decanol was investigated. In order to establish the influence of toluene concentration on the internal structure of 1,4‐DMN and DVB copolymers, surface areas, pore size distributions, and polarities of sorbents were investigated.

Angular correlations in linear copolymers from the compositional dependence of their dipole moments. V. Solvent–polymer interactions

Mean square effective dipole moments μ2e per structural unit have been determined at 298 K from a set of poly(4-chlorostyrene, 4-methylstyrene) copolymers, P (4CS,4MS), in p-xylene solutions containing 10 mole % copolymer. Coefficients which are related to local chain conformations have been evaluated from an expansion of the dipole moment ratio R (x) =μ2e(x)/μ2e(1) into a series of linearly independent functions of the mole fraction x of 4 CS units in the copolymer. The coefficient of the quadratic term, F2=1.01±0.06, obtained from these solutions is compared with the value 1.36±0.09, reported previously for the same set of copolymers in the undiluted state at 428 K. Extrapolations based on smoothed temperature coefficients which were derived from measurements in the range 360 to 440 K, yield a value F2=1.15±0.04 for the undiluted copolymers at 298 K. Uncertainties are standard deviations. It is argued that the copolymer method is relatively immune to the usual difficulties of determining dipole moments of molecules in condensed matter because it is framed in terms of ratios of experimental values of effective dipole moments. It is therefore suggested that the observed difference in values of F2 at 298 K reflects a difference in the local chain conformations resulting from the difference in the ’’solvent’’–polymer interactions in the two cases. Approximate values of the Kirkwood correlation factor g=μ2e/μ21 of P4CS, where μ1 is the moment of an equivalent freely orienting 4CS unit, are calculated from our results and compared with values obtained by others. This comparison supports the finding of Burshtein and Stepanova that g of P4CS increases toward unity as the thermodynamic quality of the solvents increase. We suggest that the copolymer method may provide a reliable means of separating a local component from the long range (excluded volume) dimensional changes that occur with changes of solvents.

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.

Vinyl ketone‐sec‐allyl alcohol copolymers–open chain‐hemiacetal ring tautomerism

AbstractThree poly(vinyl ketones) have been partially reduced to obtain different copolymers of vinyl ketones and secondary allyl alcohols. The first set of copolymers is obtained by partial reduction of poly(phenyl vinyl ketone). UV studies indicated that the Beer‐Lambert law cannot be applied to the different carbonyl bands. This is explained by a ring‐chain tautomerism between a carbonyl group and a neighboring hydroxyl group.IR and 13C NMR spectroscopy confirmed these results and proved the existence of this tautomerism.The second set of copolymers were obtained by partial reduction of poly(methyl vinyl ketone). UV showed the tautomsrism was strongly shifted toward the ring form; acetal condensation occurs in (tetrahydrofuran) THF‐methanol‐water mixture solution.The third set of copolymers obtained by partial reduction of chiral poly [(S‐2‐methyl‐butyl)vinyl ketone] were studied by UV, ORD (optical rotary dispersion), and CD (circular dichroism); all three methods giving concordant results. The tautomerism was shifted more toward the chain form than for the reduced poly(methyl vinyl ketones) but less than for reduced poly(phenyl vinyl ketones).The addition of strong acid to the polymer solution shifts the equilibrium toward the chain form; a similar shift is observed when the original polymer is in the solid state.

Acrylonitrile Copolymerizations. II. Sequence Distribution in Methyl-Methacrylate Copolymers

Abstract The distributions of the sequences of methyl methacrylate units are calculated, first by taking into account and then ignoring the effects of the penultimate units on the reactivity of the growing radicals, previously deduced from kinetic measurements. The study of the infrared and NMR spectra of a set of copolymers covering the whole range of composition does support the occurrence of these penultimate effects. Admitting these effects, it is possible to propose the assigments of several bands in the methoxy and α-methyl regions of the NMR spectra.