Polymers In High Yields Research Articles

Reproducible Superinsulation Materials: Organosilica-Based Hybrid Aerogels with Flexibility Control.

In this study, we report highly crosslinked hybrid aerogels with an organic backbone based on vinylmethyldimethoxysilane (VMDMS) with tuneable properties. For an improved and highly reproducible synthesis, a prepolymer based on 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D4V4) and VMDMS as monomers was prepared and purified. Di-tert-butylperoxide (DTBP) concentrations of 1 mol% initiate the radical polymerization of the mentioned monomers to achieve high yields of polymers. After purification, the obtained viscous polyorganosilane precursor could be reproducibly crosslinked with dimethyldimethoxysilane (DMDMS) or methyltrimethoxysilane (MTMS) to form gels in benzylic alcohol (BzOH), water (H2O) and tetramethylammonium hydroxide (TMAOH). Whereas freeze-drying these silica-based hybrid aerogels led to high thermal conductivity (>20 mW m-1K-1) and very fragile materials, useful aerogels were obtained via solvent exchange and supercritical drying with CO2. The DMDMS-based aerogels exhibit enhanced compressibility (31% at 7 kPa) and low thermal conductivity (16.5 mW m-1K-1) with densities around (0.111 g cm-3). The use of MTMS results in aerogels with lower compressibility (21% at 7 kPa) and higher density (0.124 g cm-3) but excellent insulating properties (14.8 mW m-1K-1).

Catalyst-Free synthesis of sulfonamide-functionalized Poly(phosphonate)s and Poly(phosphate)s using Bis(aziridine)s

We present an efficient step-growth polymerization method for synthesizing sulfonamide-functionalized poly(phosphonate)s and poly(phosphate)s. The polymerization process involves treating bis(aziridine) with organophosphorus acid in toluene, without the need for any catalyst, yielding the desired polymers in high yields. Six different types of organophosphorus acids and inorganic phosphoric acid were found to be suitable for this method. Thermal analysis of the resulting poly(phosphonate)s and poly(phosphate)s revealed a decomposition temperature (Td,5%) of up to 330 °C at 5 % weight loss, while differential scanning calorimetry (DSC) analysis showed glass transition temperatures (Tg) ranging from 54 to 98 °C. Microscale combustion calorimetry (MCC) analysis demonstrated that the cross-linked poly(phosphate) derived from inorganic phosphoric acid exhibited the lowest peak heat release rate (HRR) and total heat release (THR) compared to the linear ones. These findings are expected to provide a straightforward approach for synthesizing novel phosphorus-containing polymers.

Synthesis of water-soluble tetrafunctional urethane acrylate bearing a pentaerythritol core and its radical polymerization behaviors in an aqueous solution

A novel water-soluble tetrafunctional urethane acrylate (TUA) was successfully synthesized by addition reaction of pentaerythritol to 2-isocyanatoethyl acrylate. TUA efficiently underwent radical polymerization and its copolymerization with monofunctional acrylate monomers exhibiting hydrophilicity in an ethanol aqueous solution, affording corresponding networked polymers in high yields. Notably, TUA exhibited much lower volume shrinkage during the radical polymerization compared to a comparative pentaerythritol core based tetrafunctional acrylate containing no urethane bonds. The thermal decomposition temperature of the networked homopolymer, synthesized from TUA, was much higher than those of the linear polymers, synthesized from monofunctional urethane acrylate monomers. TUA is expected to be applied to the development of environmentally sustainable polymer materials.

Chiral Polymers from Norbornenes Based on Renewable Chemical Feedstocks.

Optically active polymers are of great interest as materials for dense enantioselective membranes, as well as chiral stationary phases for gas and liquid chromatography. Combining the versatility of norbornene chemistry and the advantages of chiral natural terpenes in one molecule will open up a facile route toward the synthesis of diverse optically active polymers. Herein, we prepared a set of new chiral monomers from cis-5-norbornene-2,3-dicarboxylic anhydride and chiral alcohols of various natures. Alcohols based on cyclic terpenes ((-)-menthol, (-)-borneol and pinanol), as well as commercially available alcohols (S-(-)-2-methylbutanol-1, S-(+)-3-octanol), were used. All the synthesized monomers were successfully involved in ring-opening metathesis polymerization, affording polymers in high yields (up to 96%) and with molecular weights in the range of 1.9 × 105-5.8 × 105 (Mw). The properties of the metathesis polymers obtained were studied by TGA and DSC analysis, WAXD, and circular dichroism spectroscopy. The polymers exhibited high thermal stability and good film-forming properties. Glass transition temperatures for the prepared polymers varied from -30 °C to +139 °C and, therefore, the state of the polymers changed from rubbery to glassy. The prepared polymers represent a new attractive platform of chiral polymeric materials for enantioselective membrane separation and chiral stationary phases for chromatography.

Thermal stability, pore structure characteristics of char layer and ablation resistance mechanism of new thermal insulation composites based on polyphosphazene polymer

Polyphosphazene (PDPP) composites have emerged as a hot research topic in the field of low-density composite insulation materials because of their good thermal stability and flame retardancy. In this study, the ablative properties and mechanism of PDPP composites reinforced by fiber and functional fillers are studied. The test results show that PDPP composites have good thermal stability and oxidation resistance. The results of the oxyacetylene ablation test show that PDPP composites has strong ablation resistance, and its char layer has high structural strength, as well as high bonding strength with the material matrix. However, the thermal insulation performance of PDPP composites is weak. Based on the physical and chemical analysis of the composite material and the char layer, it is concluded that the excellent ablation resistance is mainly due to the high strength of the char layer, which bnefits from high char yield of polyphosphazene polymer and the formation of silicon phosphate. However, the high thermal conductivity of composite and char layer lead to poor thermal insulation performance.

Cross‐linking reaction of diastereomeric bis‐limonene oxide with polyhydric carboxylic acid

AbstractIn this study, the epoxy‐carboxylic acid reaction was examined using two diastereomers of biobased bis‐functional epoxides (bis‐trans‐LO and bis‐cis‐LO derived from trans‐ and cis‐limonene oxide, respectively) and polyhydric carboxylic acid. The network polymers derived from bis‐trans‐LO had a higher polymer yield as well as superior thermal properties and mechanical strength than those derived from bis‐cis‐LO, since bis‐trans‐LO was cross‐linked effectively owing to the direct nucleophilic attack on the methine carbon of the epoxy ring by carboxy groups. The reprocessability of the network polymer in the presence of Zn(acac)2 was confirmed in both cases, whereas the tensile strength decreased after the 2nd cycle.

Polymer Hole Transport Materials for Perovskite Solar Cells via Buchwald–Hartwig Amination

The development of low-cost materials for charge-selective contacts that provide good energetic alignment with perovskite active layers, favorable thermal properties, and lead to efficient photoconversion is becoming an increasingly important aspect of the perovskite solar cell (PSC) field. Presented here is a series of polymers based on a one-pot polymerization of aryl dihalides with primary aryl amines to produce solution-processable polymers in high yield, with simple purification, and promising properties for high performing P-I-N PSC devices. How these properties can be tuned by careful selection of the reactant chemical moieties is discussed. Through this strategy, a wide range of relevant properties such as glass transition temperature, highest occupied molecular orbital tuning, and polydispersity are explored. When implemented into devices using a triple-cation FAMACs perovskite active layer, the hole transport material series shows average power conversion efficiencies (PCE) in excess of 17%, which is comparable to controls using state-of-the-art poly(triarylamine). How different synthetic parameters such as the reaction time and purification protocol impact device performance is also investigated.

A Bibliometric Survey on Polyisobutylene Manufacture

Polyisobutylenes (PIB) constitute a versatile family of polymer materials that have been used mainly as fuel and lubricant additives. Particularly, the current commercial demand for highly reactive polyisobutylene (HR-PIB) products motivates the development of new processes and procedures to produce PIBs with high polymer yields, narrow molar mass distributions and high vinyl contents. For this reason, a bibliometric survey is presented here to map and discuss important technical aspects and technological trends in the field of solution cationic polymerization of isobutylenes. It is shown that investigations in this field are concentrated mainly on developed countries and that industrial initiatives indicate high commercial interest and significant investments in the field. It is also shown that use of catalyst systems based on AlCl3 and ether cocatalysts can be very beneficial for PIB and HR-PIB manufacture. Finally, it is shown that investigations search for cheaper and environmentally friendly catalysts and solvents that can be employed at moderate temperatures, particularly for the production of HR-PIB.

Bimetallic nano alloy architecture on a special polymer: Ni or Cu merged with Pd for the promotion of the Mizoroki–Heck reaction and the Suzuki–Miyaura coupling

Novel Ni-Pd and Cu-Pd bimetallic nano alloys was designed and heterogenized on the highly robust ABPBI [poly(2,5-benzimidazole)] polymer in high yields using NaBH4 as reducing agent. These were versatile ligand free catalysts for the Mizoroki–Heck reaction and Suzuki–Miyaura coupling. The bimetallic Ni-Pd-ABPBI catalyst for the Mizoroki–Heck reaction of 4-iodo anisole could be recycled 5 times with high yields. Aryl bromides could also be activated for the Mizoroki–Heck reaction using Cu-Pd-ABPBI NP catalysts, with moderate yields. Synopsis Novel bimetallic Ni-Pd and Cu-Pd nano alloys, heterogenized on the robust ABPBI [poly(2,5-benzimidazole)] polymer using NaBH4 as reducing agent, is described. These were versatile ligand free, noble metal conservative catalysts, for the Mizoroki–Heck reaction and the Suzuki–Miyaura coupling. Aryl bromides were activated for the Mizoroki–Heck reaction using the Cu-Pd-ABPBI catalyst.

Trimethylscandium.

The hitherto unknown homoleptic tetramethylaluminate complex [Sc(AlMe4)3] could be obtained by reacting the ate complex [Li3ScMe6(thf)1.2] with AlMe3 in the cold. It cocrystallizes with AlMe3 as [Sc(AlMe4)3(Al2Me6)0.5] and decomposes at ambient temperature in n-pentane via multiple C-H bond activations to the mixed methyl/methylidene complex [Sc3(μ3-CH2)2(μ2-CH3)3(AlMe4)2(AlMe3)2]. Donor-induced methylaluminate cleavage of [Sc(AlMe4)3(Al2Me6)0.5] produced [ScMe3]n in good yield, which could be derivatized with trimethyltriazacyclononane (Me3TACN) to form the structurally characterizable [(Me3TACN)ScMe3]. Additionally, half-sandwich complex [Cp*Sc(AlMe4)2] and sandwich complex [Cp*2Sc(AlMe4)] were accessible by salt metathesis reactions from [Sc(AlMe4)3(Al2Me6)0.5] and KCp* (Cp* = C5Me5). 45Sc NMR spectroscopy was applied as a significant probe to evidence the existence of [ScMe3]n. Compounds [(Me3TACN)ScMe3] (+624.6 ppm) and [ScMe3(thf)x] (+601.7 ppm) gave large 45Sc NMR shifts, revealing the strong deshielding effect of the σ-bonded alkyl ligands on the scandium nuclei. Ultimately, cationized [Sc(AlMe4)3(Al2Me6)0.5] was employed in isoprene polymerization, leading to polymers in high yields (>95%) and with high (>90%) cis-1,4-polyisoprene content.

Partially biobased polymers: The synthesis of polysilylethers via dehydrocoupling catalyzed by an anionic iridium complex

Partially biobased polysilylethers (PSEs) are synthesized via dehydrocoupling polymerization catalyzed by an anionic iridium complex. Different types (AB type or AA and BB type) of monomers are suitable. Levulinic acid (LA) and succinic acid (SA) have been ranked within the top 10 chemicals derived from biomass. BB type monomers (diols) derived from LA and SA have been applied to the synthesis of PSEs. The polymerization reactions employ an air-stable anionic iridium complex bearing a functional bipyridonate ligand as catalyst. Moderate to high yields of polymers with number-average molecular weights (Mn) up to 4.38 × 104 were obtained. A possible catalytic cycle via an Ir-H species is presented. Based on the results of kinetic experiments, apparent activation energy of polymerization in the temperature range of 0–10 °C is about 38.6 kJ/mol. The PSEs synthesized from AA and BB type monomers possess good thermal stability (T5 = 418 °C to 437 °C) and low glass-transition temperature (Tg = −49.6 °C).

Ladderization of poly(p-phenylenevinylene) derivative: Synthesis of polycyclic aromatic hydrocarbon polymer by intramolecular oxidative cyclization

Poly(p-phenylenevinylene) derivative was ladderized in a stepwise manner by the intramolecular oxidative cyclization using 2,3-dichloro-5,6-dicyano-para-benzoquinone and Brønsted acids, in which the careful choice of acid was crucial for obtaining soluble ladder polymer in high yield. GPC elution time became shorter and UV–vis absorption/fluorescence emission spectra exhibited peak shifts with the progress of carbon-carbon bond formation. The ladder formation efficiency was not quantitative; however, our proof-of-concept experiment opens the door for developing novel CLPs.

Expanding the Materials Space of DNA via Organic-Phase Ring-Opening Metathesis Polymerization

Herein, we develop a facile route to bring DNA to the organic phase, which greatly expands the types of structures accessible using DNA macromonomers. Phosphotriester- and exocyclic amine-protected DNA was synthesized and further modified with a norbornene moiety, which enables homopolymerization via ring-opening metathesis to produce brush-type DNA graft polymers in high yields. Subsequent deprotection cleanly reveals the natural phosphodiester DNA. The method not only achieves high molecular weight DNA graft polymers but when carried out at low monomer:catalyst ratios, yields oligomers that can be further fractionated to molecularly pure, monodisperse entities with one through ten DNA strands per molecule. In addition, we demonstrate substantial simplification in the preparation of traditionally difficult DNA-containing structures, such as DNA/poly(ethylene glycol) diblock graft copolymers and DNA amphiphiles. We envision that the marriage of oligonucleotides with the vast range of organic-phase polymerizations will result in many new classes of materials with yet unknown properties.

Polyamide/silica hybrid materials by anionic melt polymerization of lactam-substituted silane monomers with ε-caprolactam

Polyamide 6/silica hybrid materials are fabricated by the activated anionic polymerization of ε-caprolactam (ε-CL) with lactam-substituted silane monomers Si(ε-CL)4, Me2Si(ε-CL)2 and Me3Si(ε-CL), respectively. All three silane monomers are excellent activators for the anionic ε-caprolactam polymerization initiated by EtMgBr, resulting in short reaction times of a view minutes and high polymer yields. Studies on the thermal decomposition behavior of the lactam containing silanes indicate the formation of N-iminolactams, which influence the activation process as well as the pathway of the inorganic filler formation. The molecular structure and morphology of the hybrid materials have been investigated by solution and solid-state NMR and FTIR spectroscopies as well as electron microscopy and size exclusion chromatography measurements. As consequence, lactam-substituted silane monomers serve both as activator and reactant in the synthesis of PA/silica and related hybrid materials.

Effect of Polymerization Conditions on Polypropylene Synthesis in Liquid Monomer

The effect of polymerization conditions (temperature, polymerization time, monomer and hydrogen concentrations) on propylene polymerization in the liquid monomer in the presence of a TiCl4/DBP/MgCl2 + TEA/cyclohexylmethyldimethoxysilane catalyst system is studied . It is shown that the variation of the propylene polymerization conditions in the studied ranges leads to a change in the characteristics of the resulting polypropylene. The kinetic parameters of propylene polymerization in the liquid monomer for the studied catalyst system are determined. Polymerization conditions providing the formation of polypropylene with high polymer yield, isotacticity, and bulk density values are found. The process parameters that make it possible to effectively control the molecular and rheological characteristics of polypropylene are identified.

Fast Living Polymerization and Helix-Sense-Selective Polymerization of Diazoacetates Using Air-Stable Palladium(II) Catalysts.

In this work, air-stable palladium(II) catalysts bearing bidentate phosphine ligands were designed and prepared, which could initiate fast and living polymerizations of various diazoacetate monomers under mild conditions. The polymerization afforded the desired polymers in high yields with controlled molecular weights ( Mns) and narrow molecular weight distributions ( Mw/ Mns). The Mns of the isolated polymers were linearly correlated to the initial feed ratios of monomer to catalyst, confirming the living/controlled manner of the polymerizations. The Mn also increased linearly with the monomer conversion, and all of the isolated polymers showed narrow Mw/ Mns. The polymerization was relatively fast and could be accomplished within several minutes. Such fast living polymerization method can be applied to a wide range of diazoacetate monomers in various organic solvents at room temperature in air. Taking advantage of the living nature, we facilely prepared a series of block copolymers through chain extension reactions. The amphiphilic block copolymers synthesized by this method exhibited interesting self-assembly properties. Moreover, polymerization of achiral bulky diazoacetate by Pd(II) catalysts bearing a chiral bidentate phosphine ligand leads to the formation of polymers with high optical activity due to the formation of the predominantly one-handed helix of the main chain. The helix sense of the polymers was determined by the chirality of the Pd(II) catalysts.

Neodymium versatate catalyst for the 1,3-butadiene polymerization – Effects of reaction parameters

Neodymium versatate was used as catalyst to perform solution 1,3-butadiene polymerizations. Catalysts were synthesized and aged at 5 °C for 0–60 days. Reactions were performed in the temperature range from 60 to 80 °C for 40–120 min. The obtained polymer products were characterized by Fourier-transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). It is shown that the isomers content of the final resin is sensitive to ageing and to modification of the reaction temperature in the analyzed range. Besides, aged catalysts allowed for production of polybutadienes with higher molecular weights and higher polymer yields. Finally, it is shown that chain reincorporation reactions take place when reaction is allowed to continue after reaching monomer conversions that are close to 100%.

Poly(phenylacetylene) Amines: A General Route to Water-Soluble Helical Polyamines

Poly(phenylacetylene)s bearing prim- and sec-amine groups are barely known because of their poisoning activity toward the polymerization catalyst. Herein, we prepare 11 different amino polymers in high yields by direct polymerization of their corresponding ammonium salts in water using [Rh(cod)2]+BF4– as catalyst. They are stable, water-soluble, and show a helical structure that responds to external stimuli (polarity, pH, and metal ions) acting on the pendants. The location of the amino group in the pendant is shown to be critical for the helical response to protonation.

CH Activation as a Shortcut to Conjugated Polymer Synthesis.

Direct (hetero)arylation polymerization exploits the palladium-catalyzed activation of aromatic CH bonds for the atom-economical synthesis of conjugated polymers for a wide range of applications. This account outlines how direct arylation methodologies overcome many of the limitations of contemporary polymerization techniques at both the research and production scale, and explains how monomer design and reaction conditions must be tailored to ensure high polymer molecular weight, yield, and structural integrity. Current research aims to improve further this reaction's profile as a sustainable methodology while at the same time making it competitive with the Migita-Stille and Miyaura-Suzuki polymerizations both in scope of accessible structures and synthetic efficiency. This feature article charts the recent developments and future directions of CH activation research as it moves toward becoming at once an industrially feasible, environmentally friendly, and synthetically powerful polymerization technique.

Synthesis of Poly(silyl ethers) via Iridium-Catalyzed Dehydrocoupling Polymerization

Poly(silyl ethers) (PSEs) are promising degradable materials, and the development of an efficient method to produce them from readily available materials is highly desirable. Herein, we present a dehydrocoupling polymerization of AB-type silyl alcohol monomers catalyzed by homogeneous iridium(I) complexes bearing a bisphosphine ligand. A series of PSEs containing aliphatic or aromatic linkers have been synthesized. The PDI of PSEs could be tuned by varying the ligand of iridium/bisphosphine complexes. Moderate to high yields of polymers with number-average molecular weights (Mn) up to 9.27 × 104 were obtained. The PSEs possess good thermal stability and low glass-transition temperature (Tg = −42 to −83 °C).