Silicon-containing Arylacetylene Research Articles

Design of Co-Cured Multi-Component Thermosets with Enhanced Heat Resistance, Toughness, and Processability via a Machine Learning Approach.

Designing heat-resistant thermosets with excellent comprehensive performance has been a long-standing challenge. Co-curing of various high-performance thermosets is an effective strategy, however, the traditional trial-and-error experiments have long research cycles for discovering new materials. Herein, a two-step machine learning (ML) assisted approach is proposed to design heat-resistant co-cured resins composed of polyimide (PI) and silicon-containing arylacetylene (PSA), that is, poly(silicon-alkyne imide) (PSI). First, two ML prediction models are established to evaluate the processability of PIs and their compatibility with PSA. Then, another two ML models are developed to predict the thermal decomposition temperature and flexural strength of the co-cured PSI resins. The optimal molecular structures and compositions of PSI resins are high-throughput screened. The screened PSI resins are experimentally verified to exhibit enhanced heat resistance, toughness, and processability. The research framework established in this work can be generalized to the rational design of other advanced multi-component polymeric materials.

Synthesis and properties of silicon-containing poly(diethynylbenzen-co-phenoxyphenoxybenzenediacetylene)s

Good mechanical properties, heat resistance and processability are the basic requirements of matrix resins for high performance heat resistant composites. The existing two types of silicon-containing arylacetylene resins, poly (silylene arylacetylene) (PSA) and poly (silane arylether arylacetylene) (PSEA), cannot balance these three requirements well. To achieve this goal, an attempt was made to synthesize a copolymerized resin containing both diethynylbenzene and diynyl arylether structures in the main chain, silicon-containing poly (diethynylbenzene-co-phenoxyphenoxybenzenediacetylene). By controlling the amount of 1,3-diethynylbenzene ( m-DEB) and 1,3-bis(4′-ethynylphenoxy)benzene ( pmp-BEPB), several random copolymerized resins with various ratios of m-DEB to pmp-BEPB were synthesized by the Grignard reactions. The results show that the introduction of m-DEB could effectively reduce the viscosity of the resin, and thermal stability of the cured resin is improved, but the mechanical strength of the cured resin is slightly reduced. The copolymerized resin has good overall performance when the amount of m-DEB and pmp-BEPB is equal. The processing window of the resin is 56∼169°C, the flexural strength and modulus of the cured resin are 32.9 MPa and 2.7 GPa, respectively, and the temperatures of 5% weight loss (Td5) of the cured resin is 589°C in nitrogen.

Thermal curing mechanisms and cross-linking network structure of a novel silicon-containing arylacetylene resin with 2,7-diethynylnaphthalene unit

Silicon-containing arylacetylene resin and its composites have attracted great interest as emerging heat-resistant materials, but their curing mechanisms and products are still elusive. In this work, the influences of the terminal and inner acetylenes on the curing mechanisms of silicon-containing arylacetylene resin with 2,7-diethynylnaphthalene were first identified by density functional theory. Two reaction pathways were proposed and their products include polyenes, anthracene dimers, and benzene trimers. To gain a distinct observation of the cross-linking process, molecular dynamics simulations were used to construct a cross-linking polymerization model. The effects of the temperature on the cured structure were investigated by analyzing the characteristics of the cross-linked network. As expected, higher curing temperature will make the larger proportion of polyene chain and aromatic ring in the terminal alkyne−terminal alkyne route, meanwhile, for the inner alkyne−inner alkyne route, the short chains and a small amount of aromatic rings are major productions. Overall, our cross-linking method may provide an unique guidance for studying the cured structure of other thermosetting resins.

Evaluating two stages of silicone-containing arylene resin oxidation via experiment and molecular simulation

Silicon-containing aryl acetylene resin (PSA) is a new type of high-temperature resistant resin with excellent oxidation resistance, whereas antioxidant reaction mechanism of PSA resin under ultra-high temperatures still remains unclear. Herein, the oxidation behavior and mechanisms of PSA resin are systematically investigated combining kinetic analysis and ReaxFF molecular dynamics (MD) simulations. Thermogravimetric analysis indicates that the oxidation process of PSA resin undergoes two main steps: oxidative weight gain and oxidative degradation. The Distributed Activation Energy Model (DAEM) is employed for describing oxidation processes and the best-fit one is obtained using genetic algorithms and differential evolution. DAEM model demonstrates that the oxidative weight gain stage is dominated by two virtual reactants and the oxidative degradation stage consists of three virtual reactants. Correspondingly, the observation of MD reaction pathways indicates that oxygen oxidation of unsaturated structures occurs in the initial stage, which results in the formation of PSA resin oxides. Furthermore, cracked pieces react with O2 to generate CO and other chemicals in the second step. The resin matrix's great antioxidation resilience is illustrated by the formation of SiO2. The analysis based on MD simulations exhibits an efficient computational proof with the experiments and DAEM methods. Based on the results, a two-stage reaction mechanism is proposed, which provides important theoretical support for the subsequent study of the oxidation behavior of silica-based resins.

Exploring the impact of backbone architecture on the thermal decomposition of silicon-containing arylacetylene resins

Silicon-containing arylacetylene (PSA) resins are promising heat-resistant polymers. However, little is known about their decomposition mechanisms. A molecular dynamics (MD) study based on reactive force field (ReaxFF) was employed to investigate the thermal decomposition mechanism of two representative PSA resins containing benzene or naphthalene in the backbone. The effect of heating rate, temperature, and crosslinking degree on decomposition behavior was examined, and the temperatures of three decomposition stages were disclosed. The predicted 5% decomposition temperatures (Td5) and decomposition products are consistent with experimental findings. The ReaxFF MD simulation reveals that the Td5 is dominated by the secondary decomposition and final decomposition, in which the high molecular weight and the stable CC bond of naphthyl play a dominant role in determining high-temperature resistance of the naphthalene-containing PSA resin. We also disclose the decomposition pathways of PSA-type resin. The results gained from the present work can be a helpful guideline for designing resins with excellent heat resistance.

Design of silicon-containing arylacetylene resins aided by machine learning enhanced materials genome approach

Silicon-containing acetylene resins have a broad application prospect as a type of organic–inorganic hybrid high-temperature resistant resins. However, its processability still needs further improvement to meet processing requirements for low viscosity. We proposed a materials genome approach to design and screen silicon-containing acetylene resins with excellent processing properties and heat resistance. To high-throughput screen the promising resin, we established machine learning models for predicting the properties of processing and heat resistance. Ten latent resins were screened, and one easy-to-synthesize resin was prepared by the Grignard reagent method to verify the materials genome approach. The results showed that the processing properties of the screened resin are improved evidently, with excellent heat resistance maintained. This work generates a fresh way for cost-effective data-driven designs of silicon-containing acetylene resins.

Assessing pyrolysis behavior of silicon-containing arylacetylene resin via experiments and ReaxFF MD simulations

Silicon-containing arylacetylene resin (PSA), a thermosetting organic-inorganic hybrid resin of high heat-resistance performs well in ablation process, whereas its pyrolysis behavior under high temperature has not been fully interpreted. Herein, the PSA pyrolysis process was in-depth investigated by experiments and ReaxFF molecular dynamics simulation (ReaxFF-MD). TG results show that the temperature of 5% weight loss (Td5) is above 600 ℃, and the residue at 900 ℃ surpass 85%, demonstrating PSA has excellent heat resistance and thermal stability. The on-line FTIR and out-line gas quantify analysis reveals that H2 and CH4 are dominant gaseous products, which are also unveiled by ReaxFF-MD simulation. Molecular reaction tracking indicates PSA pyrolysis is initiated by the cleavage of skeleton in benzene ring, the cleavage of C-C bond and C-Si bond in main chain at elevated temperature. Hydrogen abstraction reactions are primary formation pathways of CH4 and H2, together with conquering high energy barriers. The activation energy of PSA pyrolysis in experiments is 155 kJ/mol, agreeing well with that from ReaxFF MD simulations (144 kJ/mol), which further confirms the thermochemical stability of cured PSA that rich in highly crosslinked aromatic structure. Besides, the influence of silicon side-groups on PSA pyrolysis is screened by MD and results indicate that gases evolution depended largely on side-groups types and decreasing side phenyl groups in PSA is benefit for improving its thermal stability. This work deepens the understanding of PSA pyrolysis mechanism and provides theoretical guidance for improving its heat resistance.

Study on vinyl crosslinking and related properties of silicon-containing arylacetylene resin synthesised by zinc powder catalysis

A matrix resin poly(silicon-containing arylacetylene vinyl)s (PSAV) containing vinyl at both branch and terminal chains underwent synthesis via the zinc powder catalytic method using m-diacetylene benzene and dichloromethylvinylsilane as raw materials. Vinyl in the PSAV resin was crosslinked by the free radical initiator dibenzoyl peroxide to obtain a crosslinked network structure resin (PSAV-L). This approach sought to improve the thermal properties and other related properties of the matrix resin. A series of tests, such as rotated rheometer, FTIR, DSC, TGA, Py-GC-MS and universal testing machine, characterised processing property, curing behaviour, thermal properties and mechanical properties. The rheological curve shows that PSAV-L resin has a wide processing window (40–134.5°C), endowing the resin with excellent processing performance. Thermal curing behaviour indicates that PSAV-L resin can start curing at a lower temperature, namely, 32°C earlier than PSAV resin. TGA analysis shows that the degradation temperature at 5% weight loss (Td5) of PSAV-L resin stands at 579.4°C, 45.4°C higher than that of PSAV resin due to the fact that the crosslinking of vinyl gives PSAV-L resin a network structure. The flexural strength, flexural modulus and ILSS of the quartz fibre cloth reinforced PSAV-L resin composite (QF/PSAV-L) are 184.68 MPa, 15.50 GPa and 12.40 MPa. The PSAV-L resin exhibits the comprehensive properties of good processing performance, low curing temperature, excellent thermal performance and high mechanical properties.

Investigation of Poly(dimethylsilylene ethynylenealkylphenylenmethylenealkylphenyleneethynylene)

ABSTRACT A new kind of silicon-containing arylacetylene resins with the structure unit of ethynylenealkylphenylenemethylenealkylphenyleneethynylene in the main chains were synthesized. Their structures were characterized by 1H-NMR, FT-IR, Gel Permeation Chromatography (GPC), and X-Ray Diffraction (XRD). Properties of the resins such as solubility, softening point, viscosity, and processing window were determined. The mechanical properties and thermal stability of the cured resins and composites were tested. The results show that poly(dimethylsilylene ethynylenemethylphenylenemethylenemethylphenyleneethynylene) (PSMA-M) has good comprehensive performance. The flexural strength of the resin casting and its carbon fiber reinforced composite reaches 42.1 MPa and 381.9 MPa, respectively. The temperature (Td5) at 5% weight loss is 493°C under nitrogen.

A high-performance silicon-containing arylacetylene resin with conjugated naphthalene rings

2,7-Diphenyloxynaphthalene with large conjugated structure has been introduced into the main chain of silicon-containing arylacetylene resin and then poly(dimethylsilylene-ethynylenephenoxynaphthyloxyphenylene-ethynylene) ( m-PPNSA-MM) was synthesized. The m-PPNSA-MM resin shows good solubility and a wide processing window. A stable three-dimensional cross-linking network formed due to thermal crosslinking reactions of acetylene groups and intermolecular π–π stacking interactions after m-PPNSA-MM was cured through the process of 180°C/2 h + 220°C/2 h + 260°C/4 h. The flexural strength and modulus of the cured m-PPNSA-MM resin at room temperature are 49.2 MPa and 2.75 GPa, respectively. The cured m-PPNSA-MM resin show high thermal stabilities, the 5% temperature of weight loss ( Td5) reaches 560°C in nitrogen.

Reinforcing the poly(silylene arylacetylene)s via strong π-π stacking interactions

Silicon-containing arylacetylene resins show a trade-off between mechanical property and heat resistance as usual. A strategy is proposed by utilizing the interchain π-π stacking interactions to obtain a resin with both high mechanical property and heat resistance. In this work, silicon-containing arylacetylene resins separately with 2,5-diphenyl- [1,3,4]-oxadiazole unit as π-π stacking precursors (PODSA-MM, PODSA-MP) and the phenylene unit (PESA-MM, PESA-MP) in the main chains were synthesized by Grignard reactions. The stronger interchain π-π stacking interactions in the PODSA resins compared with PESA resins were confirmed by UV–Vis, XRD, SAXS analyses, regardless of whether or not the resins are cured. The PODSA resins with more regular structures show higher melting temperature and melt viscosity. The stable physical and chemical crosslinking dual-networks caused by both strong interchain interactions and thermal crosslinking reactions are formed in cured PODSA resins. The cured PODSA resins exhibit higher secondary relaxation temperature (Tβ), mechanical properties and thermal conductivity than cured PESA resins. The enhancement of properties of the cured PODSA resins are mainly attributed to stronger intermolecular π-π stacking interactions derived from 2,5-diphenyl- [1,3,4]-oxadiazole unit.

Effects of pendant side groups on the properties of the silicon-containing arylacetylene resins with 2,5-diphenyl-[1,3,4]-oxadiazole moieties.

Silicon-containing arylacetylene resins with rigid conjugated structures in the main chain often exhibit poor processability. A strategy of improving the processability by destroying the molecular structure symmetry using side aromatic groups was proposed, and the effects of the side groups was further explored. Two novel structural resins with side aromatic phenyl and phenylacetylene groups (PODSA-2P-MM and PODSA-2E-MM) were synthesized by Grignard reaction. The side aromatic groups strongly interfere with the regular arrangement of the main chains, and the crystallinities of the resins decrease as compared with PODSA-MM resin without side aromatic groups. Due to the influence of the side aromatic groups, the novel resins exhibit good processability, low exothermic enthalpy, high modulus and good heat resistance.

The synthesis and properties of silicon-containing arylacetylene resins with rigid-rod 2,5-diphenyl-[1,3,4]-oxadiazole moieties

The silicon-containing arylacetylene resins with 2,5-diphenyl-[1,3,4]-oxadiazole moieties (PODSA-MM, PODSA-MP and PODSA-PP) in the main chains were synthesized by Grignard reactions and characterized by protonnuclearmagneticresonance (1H NMR) spectroscopy, fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetricanalysis (TGA). The results show that the resins have good solubility, processability, low water absorption, good thermal and mechanical properties. The resins could be cured at a temperature lower than 200 °C. The flexural strength and modulus of the cured PODSA-MP resin at room temperature are 69.6 MPa and 2.5 GPa, respectively. T300 carbon fibre cloth reinforced PODSA-MP resin composite shows high flexural strength (673 MPa) and modulus (64.4 GPa) as well. The temperatures at 5% weight loss (Td5) of the cured resins are higher than 450 °C in nitrogen and air.

Developing Highly Tough, Heat-Resistant Blend Thermosets Based on Silicon-Containing Arylacetylene: A Material Genome Approach.

Silicon-containing arylacetylene (PSA) resins exhibit excellent heat resistance, yet their brittleness limits the applications. We proposed using acetylene-terminated polyimides (ATPI) as an additive to enhance the toughness of the PSA resins and maintain excellent heat resistance. A material genome approach (MGA) was first established for designing and screening the acetylene-terminated polyimides, and a polyimide named ATPI was filtered out by using this MGA. The ATPI was synthesized and blended with PSA resins to improve the toughness of the thermosets. Influences of the added ATPI contents and prepolymerization temperature on the properties were examined. The result shows that the blend resin can resist high temperature and bear excellent mechanical properties. The molecular dynamics simulations were carried out to understand the mechanism behind the improvement of toughness. The present work provides a method for the rapid design and screening of high-performance polymeric materials.

Preparation and Properties of Poly (Silicon-Containing Arylacetylene)/Attapulgite Foams

Poly(silicon-containing arylacetylene) (PSA) syntactic foams were prepared by thermally expandable microspheres (EM) in the silicon-containing arylacetylene (SA) resin during curing. The morphology, porosity, thermal and mechanical properties of the foams were studied. Furthermore, the PSA foam was reinforced by attapulgite (ATT) nanoparticles to fabricate the PSA/ATT composite foam. The results display that the density, compressive strength and thermal stability of the PSA foam decrease with increasing EM content in the matrix, but the temperature at 5% weight loss in N2 is still higher than 560°C, and the residual yield at 800°C is larger than 89%. With addition of 10 g ATT in the 100 g matrix, the average specific compressive and flexural strength of PSA/ATT foam are 31.4 MPa g-1cm3 and 33.6 MPa g-1cm3, respectively. The thermal conductivity of the composite foam can decrease to 0.064 W m-1 K-1 and has a density of 319 kg m-3.

Synthesis and application of a novel dicyanide-containing silane coupling agent

Silicon-containing arylacetylene (PSA) is a novel resin with excellent heat resistant properties and it has potential application in the field of aerospace. However, Quartz fiber(QF)/PSA composites has poor interfacial adhesion, and commonly used silane coupling agents decompose at high temperatures. In this paper, a novel silane coupling agent DCA was synthesized through the reaction of 2, 3-diamino-2-butenedioleonitrile, 2-keto-glutaric acid, 3-aminophenylacetylene and propyltriethoxysilane. In QF/PSA composites, the surface roughness and surface energy of QF had improved after modified by DCA. Spectral and thermal studies gave evidence for both homopolymerization of propargylic groups and nitrile groups during thermal curing, which indicated that DCA could co-cure with propargylic groups of PSA. After the cylization reactions of nitrile groups, a strong interfacial layer had been formed which could remarkably improve the thermal stability of composites. After modification, ILSS can reach 27.6MPa at room temperature, the retention rate was 54.7% at 500°C.

Preparation and Properties of a Novel High-Strength Foam

A novel high-strength foam (PSA foam) was prepared by adding foaming agent in silicon-containing arylacetylene (PSA) via free heat foaming. The dispersion of foaming agent was observed by Scanning Electron Microscopy-Energy Disperse Spectroscopy (SEM-EDS) and the result indicated that the foaming agent was dispersed uniformly in PSA. The microstructure of the PSA foams prepared with different foam temperatures were characterized by SEM and the results showed the PSA foam had uniform pores when the foaming temperature was 165°C. Compressive strength of the PSA foam could reach 10.3 MPa. Furthermore, PSA foam possessed excellent thermal stability, dimensional stability and heat insulation performance: char residue reached 92.3% at 800°C under nitrogen atmosphere; the highest coefficient of thermal expansion was 83*10-6/K; the thermal conductivity was 0.0724 W/(m•K).

Synthesis and characterization of silicon-containing arylacetylene ether of bisphenol a resins and their composites

Two novel resins, silicon-containing arylacetylene ether of bisphenol A (PSAP-A) and 1, 3-diethynylbenzene-terminatedsilicon-containing arylacetylene ether of bisphenol A (DPSAP-A), were synthesized from dipropargyl ether of bisphenol A (BADPE) and dimethyldichlorosilane through Grignard reaction. The structures of the resins were characterized by protonnuclearmagnetic resonance(1H-NMR), and thermal properties was explored by thermogravimetric analysis(TGA)and dynamic thermo-mechanical analysis (DMA). In addition, T300 carbon fiber(T300CF) reinforced PSAP-A composite (T300CF/PSAP-A)and T300 carbon fiber reinforced DPSAP-A composite (T300CF/DPSAP-A) were prepared by a solution-impregnation process using tetrahydrofuran as solvent. The results showed that the cured PSAP-A resin and DPSAP-A resin displayed good heat resistance and processing properties. Degradation temperatures of the cured PSPA-A resin and DPSAP-A resin at 5% weight loss (Td5) were 421.5°C and 486.3°C, respectively. The flexural strengths of T300CF/PSAP-A and T300CF/PSAP-Acomposites reached 458.2 MPa and 287.6 MPa, respectively.

Preparation and Properties of Modified Silicon-containing Arylacetylene Resin Composite Reinforced by Carbon Fiber Cloth

Preparation and Properties of Modified Silicon-containing Arylacetylene Resin Composite Reinforced by Carbon Fiber Cloth

Synthesis of Branched Silicon-Containing Arylethyleneacetylene Resin and the Performance of Casting

With good thermal properties, dielectric property and high-temperature ceramics performance, silicon-containing arylacetylene resin (PSA) has opened an attractive alternative to high performance thermosetting resins in application in the area of aircraft and missile. However, it is difficult to introduce silicon into the main chain of organic arylacetylene. In this paper, branched silicon-containing arylethyleneacetylene (BSA) resin was synthesized by methyltrichlorosilane and diethynylbenzene with zinc powder as catalyst. The advantages lie in simple operation, short reaction period and mild heat release. BSA resin exhibits excellent processability with the processing temperature of 20?C - 150?C and processing window of 130?C. The glass transition temperature of the resin casting is over 500?C. The temperature of 5% weight loss (Td5) is up to 575?C and char yield of thermoset at 800?C (Y800) reaches 91% under nitrogen. Also, the dielectric constant and dielectric loss of casting has no change within 10 - 106 Hz.