Molecular Structure Of Monomers Research Articles

Machine learning approach to polymer reaction engineering: Determining monomers reactivity ratios

In copolymerization, the monomers' reactivity ratios play an important role in shaping the final copolymer properties. Thus, the knowledge of reactivity ratio is essential to the polymer reaction engineering. However, the experimental methods of determining reactivity ratios are laborious and require many repetitions and testing at different compositions. Therefore, computational methods for determining the reactivity ratios based on the chemical structures of the reactants have attracted significant attention. Here, we demonstrate how machine learning enables the prediction of comonomers reactivity ratios based on the molecular structure of monomers. We combined multi-task learning, multi-inputs, and one of the state-of-the-art machine learning model – Graph Attention Network – to build a model capable of predicting reactivity ratios based on the monomers’ chemical structures. We found that the interpretable characteristics of Multi-Input-Multi-Output Graph Attention Network, along with its capability to learn chemical features facilitates the accurate prediction of the reactivity ratios. Such a predictive tool can be used in combination with macroscopic kinetic models to design new copolymers.

Antiwetting and low-surface-energy behavior of cardanol-based polybenzoxazine-coated cotton fabrics for oil–water separation

In the present work, the surface behavior of cotton fabrics coated with a series of bio-based polybenzoxazines is explored. Herein, we report the design and synthesis of bio-based benzoxazine monomers (C-x) using cardanol (C) and seven different amines (x = ba, ha, dda, oda, ddm, jef, and fa). The molecular structures of the benzoxazine monomers have been confirmed using FTIR and NMR analyses. The microstructure of the polybenzoxazine-coated cotton fabrics observed from FE-SEM reveals that formation of rough nanostructure is influenced by molecular structure of monomers. Further, surface analysis shows that poly(C-dda)-coated cotton fabric offers superior water contact angle (WCA = 155° ± 3) with low sliding angle (6°). Also, poly(C-dda)-coated cotton fabric delivers the lowest surface energy (14.1 mN/m) and high resistance against acidic and alkaline media. Subsequently, oil–water separation investigation shows that the poly(C-dda)-coated cotton fabric yields 99% of separation efficiency with flux value of 7200 L/m2h. Thus, the cardanol-based polybenzoxazine-coated cotton fabrics prepared in the present work can find application in the field of oil–water separation due to their superior water-repellent nature.

Synthesis, Characterization and Thermal Properties of Poly(glycidyl azide‐r‐3‐azidotetrahydrofuran) as Azido Binder for Solid Rocket Propellants

AbstractAzido polymers have been investigated as energetic binders in the area of solid rocket propellants. However, the low temperature mechanical properties of them are not comparable with the traditional propellant binders. In this work, a new kind of azido binder named poly (glycidyl azide‐r‐3‐azidotetrahydrofuran) (PGAAT) was successfully synthesized. The molecular structures of monomers and copolymers were characterized. The sensitivity and thermal properties of the azido binder were studied. The cationic copolymerization of 3‐methylsulfonyloxytetrahydrofuran with ternary cyclic ethers was confirmed. The PGAAT azido binder exhibited attractive features like low glass transition temperature (Tg, −60 °C) and high energy (1798 J/g). The results indicate that the polymer is a suitable candidate binder for the solid rocket propellants.

Experimental FTIR and FT-Raman and theoretical studies on the molecular structures of monomer and dimer of 3-thiopheneacrylic acid

This work presents an experimental and theoretical investigation on the properties of 3-thiopheneacrylic acid (3TAA) by using the FT-Raman and FT-IR spectra in the solid state. The structural, electronic, topological and vibrational properties of 3TAA were theoretically studied by using the hybrid B3LYP method with the 6-311++G (d,p) basis set. The complete assignments of the bands observed in both spectra were performed taking into account the presence of both monomer and dimer species of the acid. Two bands observed at 1682 and 1625 cm−1 attributed to the CC and CO stretching modes, respectively support the presence of the dimeric species in the solid phase. The percentages of intermolecular interactions are analyzed by Fingerprint plots of Hirshfeld surface. The natural bond orbital (NBO), atoms in molecules (AIM), frontier molecular orbitals (FMOs) and molecular electrostatic potential surface (MEPs) calculations were employed to determine the structural properties while the chemical selectivity or reactivity sites were revealed by using the Fukui functions. The GIAO and time-dependent density functional theory (TD-DFT) methods were used to predict the 1H and 13C NMR and electronic spectra of the acid. The diagrams of the density of state of that acid have been also presented. Finally, reasonable correlations between experimental and theoretical vibrational spectra were found. Effect of positioning and orientation of the acrylic group on the inhibitor characteristics on human MAOB enzyme of stable conformers of 3TAA is investigated in comparison with that of 3-2TAA and four selective inhibitors via molecular docking.

Reinvestigation of the crystal structure, vibrational spectroscopic studies and DFT calculations of 5-bromo-7-azaindole with dual N–H⋅⋅⋅N hydrogen bonds in dimers

5-Bromo-7-azaindole (5Br7AI) may act as the carrier ligand for platinum(II), in new anticancer agent, cis-[PtCl2(5Br7AI)2]. The crystal and molecular structure of the title molecule has been reinvestigated by a single crystal X-ray diffraction. The FT-IR and FT-Raman spectra of (5Br7AI) and its N-deuterated derivative have been recorded. The molecular structures of monomer and dimer, natural charges on atoms and theoretical vibrational spectra have been studied by density functional B3LYP method using 6-311++G(d,p) basis set. The results have shown that in the crystal, a pair of 5Br7AI molecules forms a centrosymmetric dimer linked by the moderately strong, dual and nearly linear N–H⋅⋅⋅N hydrogen bonds between the pyrrole and pyridine rings. The optimized geometry of the (5Br7AI)2 dimer and the calculated spectra show very good agreement with the experiment. Detailed vibrational assignments for all the species have been made on the basis of the calculated potential energy distributions (PEDs). It is concluded that a complicated spectral features of the NH (ND) stretching absorption bands are due to multiple Fermi resonances, and they are characteristic for the doubly hydrogen bonded N–H⋅⋅⋅N dimers of 7-azaindole and its halogeno derivatives.

A novel acrylic prepolymer/methacrylate modified nano-SiO2 composite used for negative photoresist

A novel nanocomposite consisting of methacrylate modified nano-SiO2 (SiO2MA) and acrylic prepolymer (G-ACP) was found a potential candidate as a negative photoresist. The SiO2MA was synthesized from glycidyl methacrylate (GMA), 3-aminpropyltriethoxysilane (KH550) and a pre-synthesized nano-SiO2 through the sol–gel process. G-ACP was synthesized through radical polymerization of five monomers, followed by grafting with carboxyl and methacrylate group. The molecular structures of monomers and polymers were characterized by FT-IR and 1H NMR spectroscopy. Finally, SiO2MA was added into G-ACP in different contents and treated with a standard thermal and UV-exposure process to obtain a series of cured organic–inorganic nanocomposite photoresists. The formed nanocomposite photoresists exhibited improved photosensitivity and had a low Dn0.5 of 26.8mJcm−2 with 13.7wt% SiO2MA. Moreover, the thermal and mechanical properties also showed great enhancement while all of the photoresists had a nice line pattern of less than 25μm.

Hydrogen bonding network in a chiral alcohol: (1R,2S,5R)-(−)-menthol. Conformational preference studied by IR–Raman–VCD spectroscopies and quantum chemical calculations

A study of the molecular structure of (1R,2S,5R)-(−)-menthol and the hydrogen bond networks formed by this species in solution is carried out. Molecular structures of monomers and H-bonded dimers and trimers of the title compound are optimized using quantum chemical calculations in the isolated molecule approach. In addition, IR, Raman and VCD techniques are used to study CCl4 solutions and thin films of the target compound. Their corresponding vibrational spectra are then analysed, both theoretically (HF and DFT) and experimentally, to characterize the different monomers (rotamers) and H-bonded oligomer species in menthol solutions as a function of the concentration.