Solid-state Polymerization Research Articles

Novel high-temperature thermochromic polydiacetylene material and its application as thermal indicator

The design and synthesis of organic high-temperature reversible thermochromic materials is one of the difficult issues in the field of organic chromic materials. In this paper, four diacetylene monomers named DBA-PCDA, TBA-PCDA, DBE-PCDA and TBE-PCDA, each containing multiple diacetylene units, were synthesized from 10,12-pentacosadiynoic acid (PCDA) through the amidation or esterification reactions, using 4,4′-diaminobiphenyl, 1,3,5-tris(4-aminophenyl)benzene, 4,4′-dihydroxybiphenyl, and 1,3,5-tris(4-hydroxyphenyl)benzene as bridging units. The effects of functional groups that can form hydrogen bond and π-π interactions on the solid-state polymerization properties of monomers and the thermochromic properties of the corresponding PDAs were investigated. The results show that only DBA-PCDA and TBA-PCDA, which contain functional groups that can form hydrogen bonding interactions, can be polymerized under 254-nm UV irradiation. The corresponding poly(DBA-PCDA) exhibits reversible thermochromic property even heated up to 200 oC, showing a potential application in the field of high-temperature thermal indicator above 100 °C. This work provides a new perspective to the development of PDA with high-temperature reversible thermochromic property.

Solid Forms of Bio-Based Monomer Salts for Polyamide 512 and Their Effect on Polymer Properties

Polyamides’ properties are greatly influenced by the polymerization process and the type of feedstock used. The solid forms of nylon salts play a significant role in determining the final characteristics of the material. This study focuses on the long-chain bio-nylon 512. Firstly, we systematically investigated the possible solid forms of the nylon 512 salt, including crystal forms and morphologies, by massive experimental screening, single-crystal X-ray diffraction, Hirshfeld surface analysis, and TG-DSC measurements. The regulation and control of the various solid forms were achieved through solid-state transformations (SSTs) and solution-mediated phase transformations (SMPTs). Our findings shows that the nylon 512 salt exists in two crystal forms (anhydrate and dihydrate) and four morphologies (needle-like, plate-like, rod-like, and massive block crystal). Many factors will influence the formation of these solid forms, such as water activity, temperature, solvent, and ultrasonic physical fields. We can choose the right factors to regulate this as needed. On this basis, we studied the effects of different solid forms (crystal forms and morphologies) on the properties of the resulting polyamides prepared using direct solid-state polymerization (DSSP). The solid form of the salt had many effects on the polymer, including its structure, melting point, and mechanical properties. The polyamide obtained through DSSP of the anhydrate salt exhibited a higher melting point (204.22 °C) and greater elastic modulus (3.366 GPa) compared to that of the dihydrate salt, especially for the anhydrate salt of plate-like crystals.

Unclicking the Click: A Depolymerizable Clicked Polymer via Two Consecutive Single-Crystal-to-Single-Crystal Reactions.

We report here a clicked polymer that can be depolymerized by a declicking reaction. A designed dipeptide monomer, upon heating its crystals, underwent a single-crystal-to-single-crystal topochemical ene-azide cycloaddition polymerization to form a triazoline-linked polymer, which upon further heating, underwent a remarkable SCSC denitrogenation, resulting in an imine-linked polymer quantitatively. As both the TEAC polymerization and the denitrogenation occurred in SCSC fashion, the structures of the triazoline-linked polymer and the imine-linked polymer could be determined at atomic resolution by SCXRD. Acid hydrolysis of the imine-linked polymer leads to quantitative depolymerization yielding a dipeptide, showcasing the degradability and depolymerizability of such polymers. This solid-state click polymerization and denitrogenation yielding depolymerizable polymer is attractive over the usual click polymers that cannot be unclicked.

Mechanochemical Synthesis of Ionic Polymers: Solid-State Ball-Milling Polymerization for Unrestricted Solubility Enabling Copolymerization of Immiscible Monomers

Mechanochemical Synthesis of Ionic Polymers: Solid-State Ball-Milling Polymerization for Unrestricted Solubility Enabling Copolymerization of Immiscible Monomers

Recent Advances in the Development of 1,4-Cyclohexanedimethanol (CHDM) and Cyclic-Monomer-Based Advanced Amorphous and Semi-Crystalline Polyesters for Smart Film Applications.

Polyester-based advanced thin films have versatile industrial applications, especially in the fields of textiles, packaging, and electronics. Recent advances in polymer science and engineering have resulted in the development of advanced amorphous and semi-crystalline polyesters with exceptional performance compared to those of conventional polymeric films. Among these, 1,4-cyclohexanedimethanol (CHDM) and cyclic-monomer-based polyesters have gained considerable attention for their exceptional characteristics and potential applications in smart films. This review article provides a comprehensive overview of the recent advances in the synthesis, characterization, and applications of CHDM and cyclic-monomer-based advanced polymers for smart film applications. It discusses the structure-property relationships of these innovative polyesters and highlights their unique characteristics, including thermal, mechanical, and barrier characteristics. Furthermore, this article also emphasizes the solution, melt, and solid-state polymerizations of the polymers. Special emphasis is placed on the influence of the addition of a second diol or second diacid on the performance characteristics of synthesized polyesters/copolyesters to explore their versatile industrial applications. Additionally, the impact of the stereochemistry of the monomers is explored to optimize the characterization of polyesters suitable for industrial applications. Furthermore, this article explores the potential of these advanced polyesters to be considered as materials for smart film applications, especially in the field of flexible electronics. Finally, this article examines the challenges and future recommendations for the development of CHDM and cyclic-monomer-based polyesters for smart film applications. It discusses potential avenues for further research, including in-depth studies for the synthesis and characterization of polyesters, the development of sustainable and biodegradable alternatives to cyclic monomers, alternative green approaches for the synthesis of polymers, etc. This review article provides valuable insight for researchers in academia and industry who are working in the fields of polymer science and materials engineering.

Catalyst free PET and PEF polyesters using a new traceless oxalate chain extender.

Plastic material performance is strongly correlated to the polymer's molecular weight. Obtaining a sufficiently high molecular weight is therefore a key goal of polymerization processes. The most important polyester polyethylene terephthalate (PET) and the new polyethylene furanoate (PEF) require metal catalysts and time-consuming production processes to reach sufficiently high molecular weights. Metal catalysts, which are typically antimony or tin for polyesters, end up in the plastic products which may result in sustainability and ecological challenges. When the less reactive comonomer isosorbide is introduced to produce (partly) biobased materials with enhanced thermal properties, such as polyethylene-co-isosorbide furanoate (PEIF), reaching high enough molecular weight becomes even more challenging. This study presents an easily implementable approach to produce high molecular weight PET and PEF polyesters and their isosorbide copolyesters PEIT and PEIF by coupling lower molecular weight polymer chains by the reactive diguaiacyl oxalate (DGO) chain extender. DGO is so reactive, that the use of metal catalysts can be completely avoided and it helps avoiding an extra solid-state polymerization step. In addition, DGO distinguishes itself from typical chain extenders by its ability to be completely removed from the resulting polymer, thereby avoiding the inherent drawbacks associated with typical chain extenders.

Complexes of copper(II), nickel(II), and cobalt(II) itaconates with chelating N-heterocycles: synthesis, structure, thermal properties, sorption activity, and their use in composites science

The reactions between copper(II), nickel(II) or cobalt(II) itaconates and N-heterocycles (2,2′-bipyridine, 1,10-phenanthroline, 4′-phenyl-2,2′:6′,2′′-terpyridine) lead to new metal-containing monomers. The complex of cobalt(II) itaconate with 4′-phenyl-2,2′:6′,2′′-terpyridine crystallizes in the triclinic form with the formula unit C52H44CoN6O10 and a molar mass of 969.85 g/mol. Unit cell parameters: a 9.02 (4) Å, b 12.52 (5) Å, c 20.68 (10) Å, α 99.64°, β 99.06°, γ 100.22 (4)°, V 2224.64 Å3, Z = 2, Z′ = 0, T = 100 K, dcalc = 1.44 g/cm3, packing factor 0.71, crystal size 0.30 × 0.32 × 0.18 mm. Each cobalt ion is coordinated by six nitrogen atoms from two 4′-phenyl-2,2′:6′,2′′-terpyridine molecules lying in mutually perpendicular planes with the formation of the CoN6 coordination site. Medium-strength hydrogen bonds including terpyridine ligands, itaconate ions, and water molecules lead to infinite one-dimensional chains. Thermolysis of the metal-containing monomers proceeds through three successive stages (dehydration, solid-state polymerization, and destruction) and makes it possible to obtain the M@C nanomaterials with the core-shell structure. The tribological characteristics of the obtained nanomaterials have been studied.

Pressure-induced phase transition and solid-state polymerization of bis(trimethylsilyl)-substituted diacetylene (BTMSDA)

Solid-state topochemical polymerization (SSTP) reactions of diacetylenes (DAs) have garnered significant attention due to their crucial role in the synthesis and development of polydiacetylenes (PDAs). However, the SSTP reaction of bis(trimethylsilyl)-substituted diacetylene (BTMSDA) has not been reported until now due to its molecular stacking parameters seriously deviating from the conditions required for the SSTP reaction. To explore the possibility of the SSTP reaction of BTMSDA under high pressure, the structural evolution of BTMSDA in the range of 0∼12 GPa was investigated using diamond anvil cells combined with in situ Raman and infrared spectroscopy techniques. During compression, BTMSDA initially underwent a phase transition from DA-Ⅰ to DA-Ⅱ around 1.2 GPa. Subsequently, BTMSDA simultaneously experienced an SSTP reaction and another phase transition around 6.5 GPa, resulting in an uneven blue mixture consisting of the PDA-blue phase of Poly-BTMSDA and the DA-Ⅲ phase of BTMSDA. Upon decompression, the uneven blue mixture transformed into an uneven red mixture comprising the PDA-red phase of Poly-BTMSDA and the DA-Ⅰ phase of BTMSDA. Analysis reveals that the phase transitions were reversible, whereas the SSTP reaction was irreversible. Moreover, the first phase transition played a pivotal role in facilitating the SSTP reaction, while the second phase transition exhibited a competitive relationship with the SSTP reaction. This study not only deepens our understanding of the physicochemical properties of BTMSDA but also demonstrates the SSTP reaction of BTMSDA under high pressure.

A novel approach for environmentally benign synthesis and solid-state polymerization of fluorinated polyimides in aqueous co-solvent

This study presents a novel approach that enables an environmentally benign water-based co-solvent synthesis of fluorinated polyimides (FPIs) using conventional fluorine-based monomers such as 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 2,2′-bis(trifluoromethyl)benzidine (TFMB). The high surface tension inherent in fluorine-based materials, which inhibits water solubility, can be overcome by mixing water with an alcohol-based solvent. The surface tension of the co-solvent decreases proportionally with the alcohol content, facilitating synthesis from fluorine-based monomers that were previously inaccessible in water. Oligomeric fluorinated poly(amic acid) salt (FPAAS) can be rapidly synthesized in aqueous solutions containing alcohol, particularly 1-propanol (PrOH). Subsequent coating and thermal treatment processes allow high molecular weight FPI films to be produced by solid-state polymerization. A comprehensive analysis of the resulting FPI films shows excellent physical properties comparable to conventionally synthesized FPI films. The 6FDA-TFMB-based FPI exhibits remarkable thermal stability up to 570 °C (Td,5%), low yellow index of 1.37, high transparency of 92.9 % and tensile strength of 116.5 MPa. The presented synthetic strategy allows the adoption of monomers with different fluorine-based substituents, thus providing insights for future aqueous synthesis. The thermal, mechanical, and optical qualities of FPIs can be utilized to create optically clear heating devices. The transparent heater, fabricated on the FPI film utilizing a laser patterning technique to create electrodes from silver nanowires, was capable of increasing the temperature up to 100 °C under a 9 V voltage application.

Dextran-based nanoparticles with 5-FU-conjugated polymethacrylate segments for drug delivery: Synthesis of amphiphilic graft copolymers by mechanochemical solid-state polymerization and characterization

Dextran (Dx) is a biodegradable and biocompatible polysaccharide, thus promising as a drug delivery carrier for tumor therapy. Herein, we applied mechanical energy to a high molecular weight Dx to control its molecular weight and simultaneously generate mechanoradicals. The solid-state polymerization of methacrylate- or methacrylamide derivatives initiated with Dx mechanoradicals showed polymer conversion of >95%, yielding Dx-based graft copolymers with molecular weights of approximately 30,000 g mol−1. The Dx-based graft copolymers with hydrophobic segments formed nanoparticles with a particle size of 25–35 nm in an aqueous solution. The anti-pancreatic tumor drug 5-fluorouracil (5-FU) was covalently conjugated onto the hydrophobic segments of the amphiphilic Dx, and the nanoparticles were also prepared. The drug release profile from 5-FU-conjugated nanoparticles corresponded well to the Korsmeyer-Peppas model applied to drug release from matrix substrates, and was also immensely predicted by the Logistic and Gompertz curves. The 5-FU-conjugated nanoparticles showed cytotoxicity against the pancreatic adenocarcinoma cell lines (BxPC-3) that were not significantly inferior to the 5-FU positive group. Furthermore, the fluorescein-labeled nanoparticles internalized into BxPC-3 within 6 h and actively migrated into the cytosol. These results suggest that Dx-based graft copolymers with hydrophobic segments might be used to enhance therapeutic activity.

Wafer-scale fabrication of mesoporous silicon functionalized with electrically conductive polymers

The fabrication of hybrid materials consisting of nanoporous hosts with conductive polymers is a challenging task, since the extreme spatial confinement often conflicts with the stringent physico-chemical requirements for polymerization of organic constituents. Here, several low-threshold and scalable synthesis routes for such hybrids are presented. First, the electrochemical synthesis of composites based on mesoporous silicon (pSi) and the polymers PANI, PPy and PEDOT is discussed and validated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Polymer filling degrees of ≥74 % are achieved. Second, the production of PEDOT/pSi hybrids, based on the solid-state polymerization (SSP) of DBEDOT to PEDOT is shown. The resulting amorphous structure of the nanopore-embedded PEDOT is investigated via in-situ synchrotron-based X-ray scattering. In addition, a twofold increase in the electrical conductivity of the hybrid compared to the porous silicon host is shown, making this system particularly promising for thermoelectric applications.

Fibre reinforced PET composite manufacturing via Solid State Polymerisation

Due to the high viscosity of thermoplastics, their processing in fibre-reinforced composite is not trivial. Here we present a route to obviate this issue in a solvent-free manner. To this purpose, we impregnate GF textiles with low-viscosity PET polymer followed by in-situ solid state polymerisation. Processing at low viscosity enables time-efficient manufacturing of void-free intermediate materials, followed by a post-processing step in the solid state that brings back the physical and chemical properties of the polymer. Via this novel approach, PET matrix inside a composite prepreg, was transformed in-situ from an oligomer of few Pas to a polymer grade with similar Mw to the highest commercially available one, in ≤10 h under mild conditions and in the solid state.

Achieving bottle‐grade poly(ethylene terephthalate)‐like properties from blends of bottle‐grade and thermoform‐grade poly(ethylene terephthalate)

AbstractPoly(ethylene terephthalate) (PET), both bottle grade (PET‐B) and thermoform grade (PET‐T), are widely used in the packaging sector. However, only PET‐B is recycled and reused, while PET‐T needs to be separated from recycled PET bales. This study aims to assess the impact of solid‐state polymerization (SSP), chain extension and the combination of chain extension–SSP to transform PET‐B and PET‐T blends into PET‐T‐like material. The intrinsic viscosity (IV) values for PET‐B blends with 10–20 wt% of PET‐T are measured for the samples obtained in this study. The mechanical properties, such as tensile strength, modulus, elongation and impact strength, were also determined. The glass transition temperature, melting temperature, crystallinity and thermal degradation were also investigated. The findings suggest that the combination of SSP and chain extension leads to a significant improvement in IV and tensile strength, while SSP alone is less suitable to offer the desired IV values. © 2024 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Solid-state nickel(0)-mediated Yamamoto coupling enabled by mechanochemistry

Abstract Herein, we report the first solid-state protocol for nickel(0)-mediated Yamamoto-coupling reactions using ball milling. A variety of aryl halides reacted efficiently in the presence of bis(cyclooctadiene)nickel(0) [Ni(cod)2] and 4,4'-di-tert-butyl-2,2'-bipyridyl under solid-state mechanochemical conditions, affording the corresponding biaryls in high yields. Considering that potentially harmful and high-boiling organic solvents are not required, the present study provides a more convenient, environmentally friendly, and sustainable alternative to conventional solution-based Yamamoto coupling. Solid-state Yamamoto-coupling polymerization and the development of a catalytic variant are also described.

Diaminomaleonitrile as a high-throughput precursor for alternative layered C=N-based conjugated polymers to carbon nitrides

In the present work, the fast production of C=N-based conjugated macrostructures from the bulk thermal polymerization of diaminomaleonitrile (DAMN) is discussed. These high-throughput syntheses showed air tolerance and were studied under different temperature regimes, from 160 to 200 °C, according to solid-state or melt polymerization (MP). This study displays not only the effect of temperature and exposure to air but also the gases evolved during the polymerization reactions. These volatiles were suitably analysed, providing relevant information about the elimination processes that take place during the course of these thermolytic reactions. The microstructure and physical properties of these black polymer materials obtained were determined by elemental analysis, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and ultraviolet–visible (UV–Vis) spectroscopies, X-ray diffraction (XRD), thermogravimetry (TG), electron paramagnetic resonance (EPR), electrochemistry measurements and scanning electron microscopy (SEM). The interpretation of all these data suggests that a two-dimensional (2-D) macrostructure based on N-heterocycles as diazines is predominant, regardless of the state of monomer aggregation during the course of the polycondensations. Interestingly, these 2-D polymeric systems present characteristic analogues with well-documented carbon nitrides (g-C3N4), with similar magnetic, electrochemical, optical and catalytic properties. Thus, DAMN polymers are proposed as alternative materials to relevant g-C3N4, as their synthetic process is easy, quick and highly efficient.

Conductive nano-Al/polyaniline composites prepared via mechanical milling

The conductive nano-Al/polyaniline composites were prepared by the milling method in the solid state. Here, aluminum nanostructures were prepared in two different mechanical methods, wire drawing and wire milling in the presence of lubricant oil. The effects of the preparation methods on the structures and morphologies of aluminum nanostructures were investigated by XRD and FESEM. The results show that the shape and size of aluminum nanoparticles in the preparation by the wire drawing method are significantly different than the wire milling method. The aluminum nanostructures were prepared by milling method have flake-like nanosheets while the wire drawing method leads to the formation of spherical ultrafine nanoparticles, which particles size are in the range of 30–60 nm. Then, polyaniline was produced using a solid-state polymerization process by the chemical reaction between aniline hydrochloride and potassium peroxydisulfate. Finally, nano-Al/polyaniline composites were prepared by mechanical milling at room temperature. The quantitative analysis was carried out with the materials analysis using diffraction (MAUD) method and weight fraction for aluminum and PANI were calculated 6.66% and 93.34%, respectively. Electrical conductivity measurements show the conductivity (1.2 × 10−2 S cm−1 at 25 °C) for polyaniline emeraldine salt and (1.02 × 10−3 S cm−1 at 25 °C) in nanocomposite respectively. The results show that by adding aluminum nanoparticles to the polymer the conductivity of nanocomposite (Al/PANI-ES) is lower than that for pure (PANI-ES). Thermogravimetry and differential thermal analysis curves show pure (PANI-ES) and nanocomposite (Al/PANI-ES) have a similar thermal degradation process. The total weight loss in TG curve of pure PANI-ES, in the temperature range 45–800 °C is 46.28% but, total weight loss observed in nanocomposite is 38.67%. Therefore, nanocomposite has higher thermal stability than that of the pure PANI-ES.

Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid-state Polymerization.

We designed a proline-derived monomer with azide and alkene functional groups to enable topochemical ene-azide cycloaddition (TEAC) polymerization. In its crystal, the monomer forms supramolecular helices along the 'a' axis through various non-covalent interactions. Along the 'c' axis, the molecules arrange themselves head-to-tail in a wave-like pattern, positioning the azide and alkene groups of adjacent molecules in close proximity and anti-parallel orientation, complying with Schmidt's criteria for topochemical reaction. This prearranged configuration was expected to facilitate smooth topochemical polymerization, resulting in a 1,4-triazoline-linked polymer. Upon heating, the monomer underwent TEAC polymerization in a remarkable single-crystal-to-single-crystal fashion, but, to our surprise, it yielded an unexpected covalent helical polymer linked by 1,5-disubstituted triazoline units. Remarkably, the crystal avoids the ready-to-react arrangement for polymerization, but connects monomer molecules within the supramolecular helix through the cycloaddition of azide and alkene groups, even though they are not in close proximity nor in the expected orientation. This unexpected path, involving a substantial 134° rotation of the alkene group, yields hitherto unknown 1,5-disubstituted triazoline product regiospecifically. This study serves as a cautionary reminder that relying solely on topochemical postulates for predicting reactivity can sometimes be misleading.

Fluorine-driven amorphous solid-state polycondensation: phosgene-free synthesis of high-molecular weight polycarbonate from fluorinated carbonate

This study presents amorphous solid-state polymerization (SSP) with fluorinated carbonate to realize efficient and facile synthesis of bisphenol-A (BPA) polycarbonate without using highly toxic phosgene gas.

Crystal-to-crystal polymerisation of monosubstituted [PW11O39Cu(H2O)]5- Keggin-type anions.

The reaction between neutral bis(picolinate)copper(II) complexes and copper(II)-monosubstituted Keggin-type phosphotungstate anions formed in situ leads to the formation of the hybrid [C(NH2)3]10[{PW11O39Cu(H2O)}2{Cu(pic)2}]·10H2O compound (1, pic = picolinate) in the presence of structure-directing guanidinium cations. Single-crystal X-ray diffraction studies demonstrate that 1 contains dimeric {PW11O39Cu(H2O)}2{Cu(pic)2} molecular species constituted by two Keggin-type anions linked by one {Cu(pic)2} octahedral complex through axial coordination to their terminal oxygen atoms. The extensive hydrogen-bonding network established by guanidium cations and Keggin clusters plays a key role in retaining the crystallinity of the system throughout dehydration to allow a single-crystal-to-single-crystal (SCSC) transformation into the anhydrous [C(NH2)3]10[{PW11O39Cu}2{Cu(pic)2}] (2a) at 170 °C. Structural modifications involve the re-orientation, shifting in ca. 1.5 Å and condensation of all the {PW11O39Cu} units to result in {PW11O39Cu}n chains in an unprecedented solid-state polymerisation. This phase transition also implies the cleavage of Cu-O bonds induced by the rotation and translation of Keggin-type anions, in such a way that hybrid dimeric units in 1 are dismantled and {Cu(pic)2} complexes become square planar. The irreversibility of the phase transition has been confirmed by combined thermal and diffractometric analyses, which evidence that the anhydrous phase adsorbs only one water molecule per cluster to become the [C(NH2)3]10[{PW11O39Cu}2{Cu(pic)2}]·2H2O (2h) hydrated derivative without any significant alteration in its cell parameters, nor in its crystalline structure. Phase transformations have been monitored by electron paramagnetic resonance spectroscopy.

A PEDOT enhanced covalent organic framework (COF) fluorescent probe for in vivo detection and imaging of Fe3+

Simple and accurate in vivo monitoring of Fe3+ is essential for gaining a better understanding of its role in physiological and pathological processes. A novel fluorescent probe was synthesized via in situ solid-state polymerization of 3,4-ethylenedioxythiophene (PEDOT) in the pore channels of a covalent organic framework (COF). The PEDOT@COF fluorescent probe exhibited an absolute quantum yield (QY) 3 times higher than COF. In the presence of Fe3+ the PEDOT@COF 475 nm fluorescence emission, 365 nm excitation, is quenched within 180 s. Fluorescence quenching is linear with Fe3+ in the concentration range of 0–960 μM, with a detection limit of 0.82 μM. The fluorescence quenching mechanism was attributed to inner filter effect (IEF), photoinduced electron transfer (PET) and static quenching (SQE) between PEDOT@COF and Fe3+. A paper strip-based detector was designed to facilitate practical applicability, and the PEDOT@COF probe successfully applied to fluorescence imaging of Fe3+ levels in vivo. This work details a tool of great promise for enabling detailed investigations into the role of Fe3+ in physiological and pathological diseases.