Solid-state Polymerization Research Articles

From blue fluorescence to red fluorescence: Solid-state oxidative coupling polymerization of fluorene and anthracene or naphthalene

Through the solid-state oxidative coupling polymerization, a series of fluorene-co-anthracene copolymer (PFA) and fluorene-co-naphthalene copolymers (PFN) were synthesized using FeCl3 as the oxidant. The structures of the copolymers were characterized by FT-IR and 1H NMR spectra, showing the random structures composed of fluorene units and 9,10-anthracene units or 1,4-linked naphthalene units. The increasing fluorene units in the backbones resulted in the increasing crystallization of copolymers by XRD patterns. All the copolymers exhibited good thermal stability. The optical properties could be adjusted by using different fluorene and anthracene or naphthalene ratios. Moreover, the polymer concentrations that affected the photoluminescence emission ranged from blue light to red light. The concentration-induced discoloration property also could be observed from the copolymers on the filter paper of TLC plates. This is attributed to the change in the effective conjugation length of a single polymer and the formation of polymer aggregates and excimers. These unique properties endow the PFA and PFN with potential applications in optoelectronics. Especially, these polymers exhibit enhanced emissions and on/off fluorescent switching which senses THF vapor efficiently.

Crystal Structures of Lignocellulosic Furfuryl Biobased Polydiacetylenes with Hydrogen-Bond Networks: Influencing the Direction of Solid-State Polymerization through Modification of the Spacer Length.

We present the topochemical polymerization of two lignocellulosic biobased diacetylenes (DAs) that only differ by an alkyl spacer length of 1 methylene (n = 1) or 3 methylene units (n = 3) between the diyne and carbamate functionalities. Their crystalline molecular organizations have the distinctive feature of being suitable for polymerization in two potential directions, either parallel or skewed to the hydrogen-bonded (HB) network. However, single-crystal structures of the final polydiacetylenes (PDAs) demonstrate that the resulting orientation of the conjugated backbones is different for these two derivatives, which lead to HB supramolecular polymer networks (2D nanosheets) for n = 1 and to independent linear PDA chains with intramolecular HBs for n = 3. Thus, spacer length modification can be considered a new strategy to influence the molecular orientation of conjugated polymer chains, which is crucial for developing the next generation of materials with optimal mechanical and optoelectronic properties. Calculations were performed on model oligodiacetylenes to evaluate the cooperativity effect of HBs in the different crystalline supramolecular packing motifs and the energy profile related to the torsion of the conjugated backbone of a PDA chain (i.e., its ability to adopt planar or helical conformations).

Spontaneous polymerization of benzofulvene derivatives bearing complexed or un-complexed pyridine rings

Benzofulvene derivatives bearing complexed and un-complexed pyridine rings are designed and synthesized to assess the effects on the spontaneous solid-state polymerization of the presence in position 6 of the 3-phenylbenzofulvene moiety of bulky substituents capable of establishing metallophilic interactions. Both the benzofulvene monomers are found to polymerize spontaneously upon solvent removal under reduced pressure in the apparent absence of catalysts or initiators. The resulting polybenzofulvene derivatives are characterized by NMR spectroscopy, MALDI-TOF mass spectrometry, and in photophysical studies.

Facile synthesis of poly(BODIPY)s via solid state polymerization and application in temperature sensor

Several 3,5-dibromo substituted BODIPY (4,4′-Difluoro-4-bora-3a,4a-diaza-s-indacene) derivatives were rationally designed and investigated as potential candidates to perform solid state polymerization (SSP). Compared with the traditional systems of thiophene and diacetylene families, which were successfully applied in SSP, SSP has been expanded to the BODIPY system in this article. In addition, crystallographic data of BODIPY derivative was derived to analyze the reasonable path of SSP, which could further explore the mechanism of SSP. Furthermore, the relationship between fluorescence intensity of BODIPY after SSP and temperature was established, which could apply this material in temperature fluorescence sensor with outstanding relative sensitivity (Sr) of 0.898% K−1. Our work has been proved to pave the way to explore more conjugated systems by using SSP method and enrich SSP database systematically.

Gamma Radiation- and Ultraviolet-Induced Polymerization of Bis(amino acid)fumaramide Gel Assemblies.

Controlling the polymerization of supramolecular self-assembly through external stimuli holds great potential for the development of responsive soft materials and manipulation at the nanoscale. Vinyl esters of bis(leu or val)fumaramide (1a and 2a) have been found to be gelators of various organic solvents and were applied in this investigation of the influence of organogelators’ self-assembly on solid-state polymerization induced by gamma and ultraviolet irradiation. Here, we report our investigation into the influences of self-assemblies of bis(amino acid vinyl ester)fumaramides on gamma-ray- and ultraviolet-induced polymerization. The gelator molecules self-assembled by non-covalent interactions, mainly through hydrogen bonds between the amide group (CONH) and the carboxyl group (COO), thus forming a gel network. NMR and FTIR spectroscopy were used to investigate and characterize supramolecular gels. TEM and SEM microscopy were used to investigate the morphology of gels and polymers. Morphology studies showed that the gels contained a filamentous structure of nanometer dimensions that was exhaustive in a three-dimensional network. The prepared derivatives contained reactive alkyl groups suitable for carrying out the polymerization reaction initiated by gamma or ultraviolet radiation in the supramolecular aggregates of selected gels. It was found that the polymerization reaction occurred only in the network of the gel and was dependent on the structure of aggregates or the proximity and orientation of double bonds in the gel network. Polymers were formed by the gels exposure to gamma and ultraviolet radiation in toluene, and water/DMF gels with transcripts of their gel structure into polymers. The polymeric material was able to immobilize various solvents by swelling. Furthermore, methyl esters of bis(leu and val)fumaramide (1b and 2b) were synthesized; these compounds showed no gelling properties, and the crystal structure of the valine derivative 2b was determined.

Structure-preserving Solid-state Thermal Huisgen Cycloaddition Polymerization of a Self-assembled Triptycene-based AB3-type Monomer

Here we present the solid-state thermal Huisgen cycloaddition polymerization of a tripodal triptycene-based AB3-type monomer (1), featuring one azide group at the bridgehead position and three alkyne groups at the 1,8,13-positions. Monomer 1 self-assembles into a “2D + 1D” structure and undergoes polymerization upon heating in the solid state without disrupting the self-assembled structure of the monomer. The resulting polymer is insoluble and likely composed of hyperbranched polymers with cyclic structures, which are highly entangled with one another to form a polycatetane network. The solid-state polymerization of a thin-film of 1 also proceeds successfully while preserving the original surface morphology at the nanoscale.

High fire-safety phosphorus-containing polyethylene terephthalate with well-balanced comprehensive performances by reactive blending with liquid crystalline copolyester

With increased public awareness of fire-safety, flame retardant materials have been widely used and developed. Among them, a polyester called CPET, synthesized by the copolymerization of polyethylene terephthalate and 2-carboxyethyl (phenyl) phosphinic acid, has a good fire-safety and has been employed in the manufacture of synthetic fibers. However, the fabricated fiber made of CPET simultaneously possessing good flame retardancy and mechanical properties is a dilemma. Herein, we resolve this problem through the reactive blending of CPET with a type of thermotropic liquid crystal copolyester (PPDT) and subsequently solid-state polymerization (SSP). Thus, the fire-safety of the CPET/PPDTSSP blend improves greatly. The peak heat release rate, total heat release, and total smoke release decrease by 31.2%, 16.3%, and 11.0%, respectively, compared with those of CPET. Meanwhile, the CPET/PPDTSSP shows better crystallization and mechanical properties than CPET. The strength at yield and Young’s modulus of CPET/PPDTSSP increase by 20.0% and 15.8%, respectively. This blend shows great potential in the fabrication of fire-safety fibers with high strength.

New Aspects on the Direct Solid State Polycondensation (DSSP) of Aliphatic Nylon Salts: The Case of Hexamethylene Diammonium Dodecanoate.

The direct solid state polymerization (DSSP) of hexamethylene diammonium dodecanoate (PA 612 salt) was investigated for two different salt grades, fossil-based and bio-based. Aliphatic polyamide salts (such as PA 612 salt) are highly susceptible to solid melt transition (SMT) phenomena, which restrain the industrial application of DSSP. To that end, emphasis was given on reactor design, being the critical parameter influencing byproduct diffusion, amine loss and inherent DSSP kinetics. Experiments took place both at the microscale and the laboratory scale, in which two different reactors were tested in terms of bypassing SMT phenomena. The new reactor designed here proved quite successful in maintaining the solid state during the reaction. Scouting experiments were conducted in order to assess the effect of critical parameters and determine appropriate reaction conditions. Fossil-based PA 612 products proved to have a better end-group imbalance in comparison to bio-based ones, which is critical in terms of achieving high molecular weight. Finally, a real DSSP process was demonstrated, starting from PA 612 salt crystals and ending with PA 612 particles.

Preparation and characterization of macrocyclic butadiyne derivatives for tubular polydiacetylenes

Ring monomers with one butadiyne moiety for solid-state polymerization, two amide groups for intermolecular hydrogen bonding, and two 3,4,5-trialkoxyphenyl groups for self-assembling and solubilization were synthesized. Depending on solvent and concentration, the monomers formed the gels. When the monomers solidified from the solutions, the structures of nanofiber aggregates were observed. The FT-IR and X-ray diffraction studies suggested that the ring monomers stacked to formed tubular nanofibers and they were bundled to form the aggregates. From the polymerization behavior monitored by visible diffuse reflectance spectra, regular 1,4-addition of butadiyne moieties was confirmed to be polydiacetylenes but its π-conjugated backbones were distorted. They did not show polymorphism in the solidification conditions performed.

Solid-state synthesis of conjugated doped poly(3,4-ethylenedioxythiophene): An effective adsorbent for selective anionic dye removal

In this work, we report the adsorption studies of dyes using as-prepared doped poly(3,4-ethylenedioxythiophene) (PEDOT). The conjugated polymer PEDOT was prepared by the solid-state polymerization method and used as an effective adsorbent for the removal of various dyes from aqueous solution. It was found that the as-prepared PEDOT adsorbs selective anionic dyes, whereas no significant adsorption was observed for cationic dyes. The effect of concentration of eriochrome black T (EBT) dye on time-dependent adsorption was studied. Like doped PEDOT, de-doped PEDOT was examined with different concentrations of EBT dye solutions and observed poor adsorption. The adsorption kinetics and isotherms for doped and de-doped PEDOT were studied. The morphology and elemental composition of doped PEDOT before and after adsorption were analyzed by scanning electron microscopy and energy-dispersive X-ray, respectively. Further, the effectiveness of as-prepared doped polymer PEDOT as an adsorbent for EBT dye from organic solvents (ethanol, DMSO, acetonitrile and DMF) was carried out.

Anisotropic Synthetic Allomelanin Materials via Solid-State Polymerization of Self-Assembled 1,8-Dihydroxynaphthalene Dimers.

Melanosomes in nature have diverse morphologies, including spheres, rods, and platelets. By contrast, shapes of synthetic melanins have been almost entirely limited to spherical nanoparticles with few exceptions produced by complex templated synthetic methods. Here, we report a non-templated method to access synthetic melanins with a variety of architectures including spheres, sheets, and platelets. Three 1,8-dihydroxynaphthalene dimers (4-4', 2-4' and 2-2') were used as self-assembling synthons. These dimers pack to form well-defined structures of varying morphologies depending on the isomer. Specifically, distinctive ellipsoidal platelets can be obtained using 4-4' dimers. Solid-state polymerization of the preorganized dimers generates polymeric synthetic melanins while maintaining the initial particle morphologies. This work provides a new route to anisotropic synthetic melanins, where the building blocks are preorganized into specific shapes, followed by solid-state polymerization.

Evidence of Solid-State Polymerization in Regioregular Poly-3′,4′-Didodecyl-2,2′:5′,2′′-Terthiophene During Electrochemical Cycling

The electrochemical oxidation of 3′,4′-didodecyl-2,2′:5′,2′′-terthiophene (3′4′-DDTT) at applied potential values lower than 0.8 V vs Ag/Ag+ leads to the formation of an anodic deposit that is prevalently constituted by the products of monomer coupling at positions 5 and 5′′. Upon electrochemical cycling poly-3′4′-DDTT manifests three phenomena: the cathodic shift of the main peak of poly-3′4′-DDTT oxidation, the bathochromic shift of 60 nm for the main UV–vis absorption peak, and the IR spectral evolution consisting of the progressive increase of the signals of 2,5-substituted thiophenes at expense of the signals from 2-substituted thiophenes. The observed behavior was interpreted in terms of the presence of reactive oligomers trapped in pristine as-deposited poly-3′4′-DDTT, with the oligomers undergoing further coupling in the polymeric phase upon electrochemical cycling. This combination of findings led us to conclude that poly-3′4′-DDTT manifests solid-state polymerization. After voltammogram stabilization poly-3′4′-DDTT was electrochemically stressed. The system showed a reversible electrochemical behavior up to 0.9 V vs Ag/Ag+. A depiction of the evolution of the electronic bands in poly-3′4′-DDTT when passing from the pristine state to the electrochemically cycled state has been proposed, taking into account the combination of electrochemical and optical data.

Polybenzimidazoles as proton exchange membrane in fuel cell applications

As the world’s transportation is seeking to switch towards renewable and sustainable sources of energy, the research in fuel cell technology has gained momentum. Proton exchange membrane fuel cell (PEMFC) operating at temperature range 100–200°C (high-temperature proton exchange membrane fuel cells, HT-PEMFCs) has gained interest in their major application to electric power generation. The most promising material is polybenzimidazoles (PBI). Synthesis methods such as condensation polymerization, solid-state or melt polymerization, etc. give the polymer with different inherent viscosity. The monomer modifications both in tetramine and the diacid, reveal variations in glass transition value. Further insight into the membrane casting solvents and methods along with its proton conductivity has been reviewed. Review paper is comprising of Part 1: for the synthesis methods, structural changes, and applications of PBIs in HT-PEMFCs while, Part 2: for the various kinds of PBIs has been discussed.[Formula: see text]

Evaluation of the Technical Viability of Distributed Mechanical Recycling of PLA 3D Printing Wastes.

3D printing PLA wastes were recovered from a well-known reference grade and from different sources. The recovered wastes were subjected to an energic washing step and then reprocessed into films by melt-extrusion, followed by compression molding to simulate the industrial processing conditions. The obtained materials were characterized and the optical, structural, thermal and crystallization behavior are reported. The mechanical recycling process leads to an increase of the crystallinity and a decrease of the intrinsic viscosity of the formulations, particularly in the sample based on blends of different 3D-PLA wastes. Moreover, the obtained films were disintegrated under composting conditions in less than one month and it was observed that recycled materials degrade somewhat faster than the starting 3D-PLA filament, as a consequence of the presence of shorter polymer chains. Finally, to increase the molecular weight of the recycled materials, the 3D-PLA wastes were submitted to a solid-state polymerization process at 110, 120, and 130 °C, observing that the recycled 3D-wastes materials based on a well-known reference grade experiences an improvement of the intrinsic viscosity, while that coming from different sources showed no significant changes. Thus, the results show that 3D printing PLA products provides an ideal environment for the implementation of distributed recycling program, in which wastes coming from well-known PLA grades can successfully be processed in films with good overall performance.

Synthesis of hexagonal rosettes of g-C3N4 with boosted charge transfer for the enhanced visible-light photocatalytic hydrogen evolution and hydrogen peroxide production

Photocatalytic sustainable fuel production attracted extensive attention because of the urgent need of the society to shift from fossil fuels to solar fuels. Herein, the synthesis of hexagonal rosettes of g-C3N4 with an efficient performance toward hydrogen evolution and hydrogen peroxide production as the two kinds of solar fuels were reported. The hexagonal rosettes of g-C3N4 were simply fabricated via controlled solid-state polymerization of three-dimensional hexagonal rosettes of cyanuric acid-melamine adduct at 500 °C. The hexagonal rosettes of g-C3N4 showed an amorphous nature with an extremely high surface area of 400 m2 g−1. Also, the as-obtained catalyst demonstrated remarkable photocatalytic activity in hydrogen production of 1285 μmol g−1 h−1 and hydrogen peroxide production of 150 μmol g−1 h−1. The mechanism for the polymerization process of the cyanuric acid-melamine (CM) complex to hexagonal rosettes of g-C3N4 was thoroughly described employing electron microscopy tools. This study identified that the CM complex condensation is accomplished via a dehydration process by producing a highly condensed and active structure of g-C3N4, which is different from the previously reported condensation mechanism of the melamine and its derivatives performed through a deamination process.

Solid-state polymerization of diaminomaleonitrile: Toward a new generation of conjugated functional materials

The solid-state polymerization (SSP) of organic molecules to form two-dimensional (2D) materials remains a challenge, especially when these reactions are performed in one pot using a single reagent. As will be shown, the SSP of the HCN tetramer diaminomaleonitrile (DAMN) may be an excellent example of these reactions. Dynamic experiments by differential scanning calorimetry (DSC) allow the analysis of the thermally initiated bulk polymerization of DAMN. Under nonisothermal measurements at low heating rates, a multiple-step polymerization reaction takes place. The SSP of DAMN is highly efficient, possibly due to the autocatalytic nature of its kinetics, which are consistent with the two-parameter Šesták-Berggren (SB) model and describe the three stages found in its complicated mechanism, confirmed also from an analysis of the variation in the apparent activation energy with the conversion degree. Relevant mechanistic aspects, such as the dehydrocyanation and deamination processes during SSP, are extracted by thermogravimetry-mass spectrometry (TG-MS). Moreover, some structural and morphological properties of these materials are characterized by Fourier-transform infrared (FTIR) spectroscopy and microscopy. All this information allows us to propose hypothetical pathways for the production of a complex conjugated system, predominantly constituted by a 2D macrostructure based on imidazole rings. This work opens up new possibilities for the synthesis of functional poly(heterocycle) systems, expanding our view of a plausible prebiotic chemical reaction space and providing the foundation for systematic studies of the structure-property relationships of novel HCN-derived polymers, which are currently of great interest in the fields of materials and surface science.

2,5-Dibromothiophenes: Halogen Bond Involving Packing Patterns and Their Relevance to Solid-State Polymerization

A series of 2,5-dibromo-3-R-thiophenes (R = COONa 1, CN 2, CONH2 3, CON(H)Me 4, CON(H)Bn 5, CON(CH2CH2)2O 6, CON(H)NH2 7, CON(H)OH 8) were prepared and studied via high-resolution ESI-MS, 1H and 13...

Bio-based poly(pentamethylene sebacamide) by solid-state polymerization from bio-based monomers

Solid-state polymerization (SSP) of biocadaverine and biosebacic acid monomers produced PA510 bioplastic having low water absorption (0.18%) and low oxygen permeability (1.47 cc mm m−2 day) compared to other long chain polyamides.

Solid-State Polymerization as a Vitrimerization Tool Starting from Available Thermoplastics: The Effect of Reaction Temperature.

In the current work, solid-state polymerization (SSP) was studied for the synthesis of poly(butylene terephthalate), PBT-based vitrimers. A two-step process was followed; the first step involved alcoholysis reactions and the incorporation of glycerol in the polymer chains. The second step comprised transesterification reactions in the solid state (SSP) in the presence of zinc(II) catalyst resulting in the formation of a dynamic crosslinked network with glycerol moieties serving as the crosslinkers. The optimum SSP conditions were found to be 3 h at 180 °C under N2 flow (0.5 L/min) to reach high vitrimer insolubility (up to 75%) and melt strength (2.1 times reduction in the melt flow rate) while increasing the crosslinker concentration (from 3.5 to 7 wt.%) improved further the properties. Glass transition temperature (Tg) was almost tripled in vitrimers compared to initial thermoplastic, reaching a maximum of 97 °C, whereas the melting point (Tm) was slightly decreased, due to loss of symmetry perfection under the influence of the crosslinks. Moreover, the effect of the dynamic crosslinked structure on PBT crystallization behavior was investigated in detail by studying the kinetics of non-isothermal crystallization. The calculated effective activation energy using the Kissinger model and the nucleating activity revealed that the higher crosslinker content impeded and slowed down vitrimers melt crystallization, also inducing an alteration in the crystallization mechanism towards sporadic heterogeneous growth.

Towards High Molecular Weight Furan-Based Polyesters: Solid State Polymerization Study of Bio-Based Poly(Propylene Furanoate) and Poly(Butylene Furanoate).

In the era of polymers from renewable resources, polyesters derived from 2,5 furan dicarboxylic acid (FDCA) have received increasing attention due to their outstanding features. To commercialize them, it is necessary to synthesize high molecular weight polymers through efficient and simple methods. In this study, two furan-based polyesters, namely poly (propylene furanoate) (PPF) and poly(butylene furanoate) (PBF), were synthesized with the conventional two-step melt polycondensation, followed by solid-state polycondensation (SSP) conducted at different temperatures and reaction times. Molecular weight, structure and thermal properties were measured for all resultant polyesters. As expected, increasing SSP time and temperature results in polymers with increased intrinsic viscosity (IV), increased molecular weight and reduced carboxyl end-group content. Finally, those results were used to generate a simple mathematical model that prognosticates the time evolution of the materials’ IV and end groups concentration during SSP.