Tg Of Polymer Research Articles

Scanning Electron Microscopy and Raman Spectroscopy Characterization of Structural Changes Induced by Thermal Treatment in Innovative Bio-Based Polyamide Nanocomposites

A comprehensive Raman scattering-based characterization of a full bio-based polyamide loaded with graphene nanoplatelets or layered double hydroxides (LDH) was assessed. The potential of the Raman spectroscopy was used to reveal several particularities of the nanocomposite structures induced by thermal treatment. Thus, a complete morpho-structural picture was obtained in combination with scanning electron microscopy (SEM) analysis of the neat polyamide and polyamide nanocomposites exposed at different thermal conditions (room temperature, 80 °C, and 145 °C). The analysis of G, D and 2D Raman peaks and their relative intensity ratio ID/IG, revealed the fact that the presence of graphene in polyamide is suitable for improving the essential physical properties and is also responsible for the decrease in the defects’ occurrence in the graphene layers. The surface of nanocomposites based on full bio-based polyamide, with different 2D fillers (graphenic and non-graphenic structures), was carefully evaluated before and after the thermal treatment by employing SEM and Raman analyses. The two thermal treatments allowed different chain mobility of the polymer (first temperature being over the polymer Tg and second one close to the melting phase in the viscoelastic stage). The spectroscopic and microscopic investigation was used to determine the conformational changes in filler aggregates and polymer surface, respectively.

Influence of quadruple hydrogen bonding on polyvinyl butyral resin properties

Herein we report an easily accessible supramolecular polymer readily made from polyvinyl butyral (PVB) by cross-linking with non-covalent self-complementary ureido-pyrimidinone (UPy) dimers. The resulting materials exhibit multifunctional properties, not only self-healing and shape memory, but also enhanced thermo-mechanical resistance. The UPy content, which represents the quadruple hydrogen bonding density, shows an important influence on tuning polymer performances. Moderate UPy content (2.5 mol.%) is important to impart the optimal comprehensive properties. Both infrared analyses and dynamic mechanical analyses indicate that the quadruple hydrogen bonding is stable up to 120 °C, thus enabling the healing process. The healing efficiency highly depends on the glass transition temperature (Tg) of the final polymer, itself being controlled by the UPy content. A 100% healing efficiency can be achieved at 120 °C when the UPy content is controlled up to 2.5 mol.%. Meanwhile, around 90% healing efficiency was achieved in water at 60 °C for all materials. All samples exhibit shape memory properties without obvious dependence on the UPy content. This work illustrates that the physical cross-linking, formed by non-covalent hydrogen bonding, cannot only provide a practical strategy to obtain multi-responsive shape memory polymers with self-healing feature but also offers the possibility to tune the polymer thermal and mechanical properties.

Molecular dynamics simulations on photoinduced switchable Tg and self-healing behaviors of azobenzene-containing polymers

Developing polymers with switchable glass transition temperature (Tg) can solve scientific challenges such as fracture healing of polymers with high Tg and processing of hard polymers without plasticizer at room temperature. The azobenzene-containing polymers, or the so-called azopolymers, are smart materials that show photoswitchable Tg and photoinduced motions, which can be used in fabrication of photoactuators. Here, healable and reprocessable models were constructed by using linear azopolymers. Molecular dynamics (MD) simulation was used to study the behaviors of photo-induced bending, self-healing, and directional photofluidization of the azopolymers. A temporary modification of the C–N=N–C dihedral potential was applied to achieve the isomerization of azopolymer by using polymer consistent force-field (PCFF). The simulation results show that isomerization of azobenzene groups can lead to photoswitchable Tg of the azopolymers, which resulting in shape changes and different mechanical responses. Furthermore, the photoswitchable Tg makes the azopolymers much easier to heal under UV irradiation, and restore the mechanical properties under visible light irradiation. Finally, the mechanism of photoliquefaction was investigated, our results imply that the photoinduced trans–cis-trans cycles can reduce the mechanical properties and Tg values of azopolymers.

Hydrophobic hydrogels as internal curing agent for concrete: The double benefit of super high water content and excellent anti-ion permeability

Owing to their high water content, conventional superabsorbent polymer (SAP) hydrogels can serve as internal curing agents for concrete fabrication. However, the hydrophilic network in such hydrogels permits ion diffusion, which induces severe steel corrosion inside concrete in the marine environment. Herein, we introduce a brand-new hydrogel, termed “hydrophobic hydrogels”, for concrete curing. On one hand, these hydrogels possess super high water content (up to 99.6 wt%), which is even higher than that in normal SAP hydrogels; on the other hand, the anhydrous inhomogeneous hydrophobic structures can significantly retard or stop the ion permeation, which is significantly superior to SAP hydrogels. With ion diffusion measurement, the hydrophobic hydrogels achieve much better ion resistance than SAP hydrogels, with 2–5 orders' decrease in ion permeation rate. Among diverse hydrophobic hydrogels, the polymer's hydrophobicity and glass transition directly determine the permeation performance. Hydrogels with a more hydrophobic network and higher polymer Tg possess better anti-ion diffusion properties. At the optimal state, the poly(phenyl acrylate) hydrophobic hydrogels can completely stop the permeation process. Owing to the double benefit, the hydrophobic hydrogel cured concretes demonstrate a notable decrease in ion permeation compared to SAP hydrogel cured concrete, with only 1/20 of ion permeation to that in SAP groups with an electric flux test upon coated on the surface layers. Owing to the double benefit from super high water content and excellent anti-ion permeability, these hydrophobic hydrogels may serve as ideal candidates as concrete curing agents in the future.

Investigation of thermal, antibacterial and heavy metal ion removal behavior of polyamide/polyimide iron oxide nanocomposites

In this study, a newly-designed diamine (DA) containing pyridine and carbazole groups was synthesized and the relevant polyamides (PAs) and polyimides (PIs) were prepared by polymerization reaction between the DA monomer and terephthalic acid, adipic acid, and pyromellitic dianhydride. In addition, polymer nanocomposites were prepared through a combination of the synthesized polymers with modified magnetite iron oxide nanoparticles. The synthesized compounds were fully characterized by hydrogen nuclear magnetic resonance (1HNMR), fourier-transform infrared (FTIR), field emitting scanning electron microscopy (FESEM), energy dispersive X-Ray (EDX), Transmission electron microscopy (TEM), Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) analyses. All of the synthesized properties of compounds such as thermal stability, viscosity, elimination capability of heavy metals ions adsorption, and antibacterial activity were investigated. Polyamides and PI showed good solubility in aprotic solvents and the viscosity was in the range of 0.72–0.89 dL/g. Also, the glass-transition temperature (Tg) of synthetic polymers was in the range of 214–273°C and 10% weight loss temperatures (T10%) for the synthesized compounds were in the temperature range of 280–492°C in N2, and the percentage of residual ash between 61 and 74%. The adsorption rate of Hg2+, Co2+, Pb2+, Cr2+, and Cd2+ metal ions by PA containing terephthalic acid (PAT) and its nanocomposite (NCPAT) showed that nanocomposite has a better performance compared to PAT. The highest and lowest removal efficiency was related to Hg2+ and Pb2+ ion, respectively. Finally, antibacterial test results against Gram-positive and Gram-negative bacteria showed favorable inhibitory effects of all the synthesized polymers.

Expanding the Scope of RAFT Multiblock Copolymer Synthesis Using the Nanoreactor Concept: The Critical Importance of Initiator Hydrophobicity

Precise multiblock copolymer synthesis coupled with self-assembly offers morphology control on length scales ranging from a few nanometers to micrometer scale, providing enormous opportunities for future development of advanced materials and applications. The scope of multiblock copolymer synthesis via RAFT polymerization has recently been expanded by application of the nanoreactor concept for emulsion polymerization. This enabled use of slow propagating monomers, such as styrenes and methacrylates, in multiblock synthesis. However, severe limitations attributed to the high polymer glass transition temperature (Tg) of some polymers have hitherto remained. The use of monomers that give such high-Tg polymers effectively prevented penetration of aqueous-phase-generated radicals into the polymer particles wherein the RAFT functionality is located. We here demonstrate that these constraints can be relieved by judicious choice of the radical initiator. Multiblock homopolymers were synthesized by seeded RAFT emulsion polymerization using initiators that differ substantially in hydrophobicity. Ten sequential chain extensions using tert-butyl methacrylate (Tg of PtBMA = 118 °C) with targeted block DP = 100 were conducted at 80 °C for each initiator. Markedly narrower molecular weight distributions were obtained when more hydrophobic initiators were used. The same polymerizations targeting low -Tg polymers (PnBMA; Tg = 20 °C) resulted in only minor differences in control when the different initiators were used, supporting our hypothesis on the role of radical penetration. The present results are anticipated to significantly expand the scope of RAFT polymerization in aqueous emulsion by allowing access to a wider range of low-dispersity multiblock copolymers.

Robust strategies to reduce burst and achieve tunable control over extended drug release from uniaxially electrospun composites

In this study, robust strategies were developed to prepare uniaxially electrospun composites that reduced initial burst and provided controlled release of budesonide (a clinically important corticosteroid) over an extended timeframe in vitro. First, poly(caprolactone) (PCL) meshes were shown to exhibit significant burst while poly(D,L-lactide-co-glycolide) 85:15 (PLGA) meshes intrinsically promoted zero-order release over 28d. In-depth characterization of the architectural, physico-chemical and thermal properties revealed differences in gross morphological behavior, water uptake capacity, polymer Tg, and drug affinity to the matrix as factors governing release. Based on this mechanistic understanding of release from fast- and slow-releasing polymers, PCL and PLGA were next judiciously blended in a specific ratio i.e., 20PCL/80PLGA to achieve controlled first-order release over 28d at a faster rate than PLGA but without an initial burst. Interestingly, increasing the PCL content to 30% (i.e., a 30PCL/70PLGA blend) resulted in a sharp burst release. Since the release from the 30PCL/70PLGA blend depended on intrinsic system characteristics, a dual-spinneret co-electrospinning approach was employed to effectively decouple fiber properties and achieve precise drug distribution across independently integrated PCL and PLGA fibers. Consequently, the co-electrospun meshes — possessing identical polymer compositions and drug/polymer ratios as the 30PCL/70PLGA blend — exhibited no burst and resulted in predictable release characterized by 10d zero-order kinetics. Notably, neither the rationally guided blending nor the co-electrospinning strategy involved the use of cytotoxic cross-linkers, bioactivity-reducing excipients, delamination-prone barrier layers and complex set-ups. Based on the application, a rational choice of blend ratios or co-electrospinning parameters may be used to tune the rate of release from the composites.

Moisture sorption by polymeric excipients commonly used in amorphous solid dispersion and its effect on glass transition temperature: I. Polyvinylpyrrolidone and related copolymers

Moisture plays a critical role in the stability of amorphous solid dispersions (ASD) as it can lower the glass transition temperature (Tg) and thereby increase molecular mobility resulting in drug crystallization. A systematic study on moisture sorption by four polyvinylpyrrolidone (PVP) having different molecular weights (Kollidon® 12, 17, 30, and 90) and two related copolymers (Kollidon® VA64; Soluplus®) was conducted at 25 and 40 °C as a function of relative humidity to determine effects of absorbed moisture on Tg and potential stability of ASDs. A VTI dynamic moisture sorption analyzer was used, where experimental conditions were first established such that equilibrium was reached and there was no significant hysteresis loop between sorption and desorption isotherms. The PVPs had identical moisture sorption profiles and were highly hygroscopic, reaching 22–24% and 41–42% w/w moisture at 25 °C/60% RH and 25 °C/80% RH, respectively. Kollidon® VA64 and Soluplus® were relatively less hygroscopic, reaching, respectively, about half and one-fourth the moisture content of PVPs at 25 °C/60% RH. Moisture sorption at 40 °C was relatively lower than that at 25 °C. The high moisture sorption drastically decreased Tg of polymers, which roughly agreed with theoretical calculations based on the Gordon-Taylor/Kelley-Bueche equation, although deviation occurred, possibly due to hydrogen bonding between polymer and moisture.

Versatile strategies to tailor the glass transition temperatures of bottlebrush polymers

The glass transition temperature (Tg) of bottlebrush polymers can be controlledviaside-chain length, blend composition and brush topology. Elucidating interactions between these parameters and their design rules enables accurate targeting ofTgat arbitrary molecular weights.

RAFT Polymerization of a Renewable Ricinoleic Acid‐Derived Monomer and Subsequent Post‐Polymerization Modification via the Biginelli‐3‐Component Reaction

AbstractThe search for renewable monomers for radical polymerization techniques is of current interest due to the awareness of sustainability requirements in the chemical sciences. Herein, the synthesis and reversible addition‐fragmentation chain‐transfer (RAFT) polymerization of a renewable methacrylate monomer based on ricinoleic acid as sustainable starting material is presented. In addition, the hydroxy moiety of the ricinoleic acid is converted to an acetoacetate in order to allow for a post‐polymerization modification (PPM) using the Biginelli‐three‐component reaction (B‐3CR), rendering the presented monomer a renewable and highly flexible reactant for the synthesis of polymer materials. Consequently, RAFT polymerization yields macromolecules with a molecular weight of up to 15 000 g mol−1 and expectedly narrow molecular weight distributions with Ðs around 1.13. The feasibility of chain extension and block copolymer synthesis is demonstrated. Eventually, the PPM of the acetoacetate moiety of the polymer repeating units using the B‐3CR is proven to be efficient with conversions of up to 95% of the acetoacetates, while the modification allows for a pronounced increase of the glass transition temperature to approximately room temperature compared to the unmodified polymers (Tg = −50 °C).

Wetting properties and morphological behavior of core-shell polymer-based nanoparticle coatings

The glass transition temperature (Tg) strongly affects the physicochemical properties of a polymer. In particular, coating a material with polymer nanocapsules with two or more Tg values can endow the material with variety of properties. We introduced polymer nanocapsules onto glass substrates and analyzed the effect of polymer Tg on the surface properties of the coating. Core-shell polymer (CSP) particles were prepared by a two-step emulsion polymerization procedure using poly(methyl methacrylate) (PMMA, Tg = 105 °C) and poly(butyl acrylate) (PBA, Tg = −54 °C) in different ratios as cores, and poly(nonafluorohexyl acrylate) (PNFHA, Tg = −6 °C) as shells. The microstructural and microbehavioral properties of the coating surface were found to depend on the Tgs of the synthesized CSP. Surface elemental distributions and chemical bonding were analyzed by XPS depth profiling to determine the behavior of the CSP nanoparticles. A core/shell nanoparticle with Tg = 55.81/−9.12 °C has a high probability of its core becoming located at the coating surface. On the other hand, a core/shell nanoparticle with Tg = −33.17.81/−28.6 °C has a high probability of its shell becoming located at the surface. Because the shell has a low surface energy, test solutions with a variety of surface tensions exhibited low wettabilities. These results allow the Tg values of the CSP to access the final thermodynamic equilibrium state, reveal that the Tg values affect the surface distribution of the functional groups of the coatings, which in turn determine its surface morphology and wetting properties.

Room-Temperature Self-Healable and Mechanically Robust Thermoset Polymers for Healing Delamination and Recycling Carbon Fibers.

The advocacy of carbon neutrality and circular economy encourages people to pursue self-healing and recycling of glassy thermoset polymers in a more realistic and energy-saving manner, the best being intrinsic healing under room temperature. However, the high mechanical robustness and healing ability are mutually exclusive because of their completely opposite requirements for the mobility of the polymer networks. Here, we report a dual-cross-linked network by slightly coupling the low-molecular-weight branched polyethylenimine with an ester-containing epoxy monomer in a nonstoichiometric proportion. The highly mobile and dense noncovalent hydrogen bonds at the chain branches and ends can not only complement the mechanical robustness (tensile strength of 61.6 MPa, elastic modulus of 1.6 GPa, and toughness of 19.2 MJ/m3) but also endow the glassy thermoset polymer (Tg > 40 °C) with intrinsic self-healing ability (healing efficiency > 84%) at 20 °C. Moreover, the resultant covalent adaptive network makes the thermoset polymer stable to high temperatures and solvents, yet it is readily dissolved in ethylene glycol through internal catalyzed transesterification. The application to room temperature delamination healing and carbon fiber recycling was demonstrated as a proof-of-concept.

Benchmarking Machine Learning Models for Polymer Informatics: An Example of Glass Transition Temperature.

In the field of polymer informatics, utilizing machine learning (ML) techniques to evaluate the glass transition temperature Tg and other properties of polymers has attracted extensive attention. This data-centric approach is much more efficient and practical than the laborious experimental measurements when encountered a daunting number of polymer structures. Various ML models are demonstrated to perform well for Tg prediction. Nevertheless, they are trained on different data sets, using different structure representations, and based on different feature engineering methods. Thus, the critical question arises on selecting a proper ML model to better handle the Tg prediction with generalization ability. To provide a fair comparison of different ML techniques and examine the key factors that affect the model performance, we carry out a systematic benchmark study by compiling 79 different ML models and training them on a large and diverse data set. The three major components in setting up an ML model are structure representations, feature representations, and ML algorithms. In terms of polymer structure representation, we consider the polymer monomer, repeat unit, and oligomer with longer chain structure. Based on that feature, representation is calculated, including Morgan fingerprinting with or without substructure frequency, RDKit descriptors, molecular embedding, molecular graph, etc. Afterward, the obtained feature input is trained using different ML algorithms, such as deep neural networks, convolutional neural networks, random forest, support vector machine, LASSO regression, and Gaussian process regression. We evaluate the performance of these ML models using a holdout test set and an extra unlabeled data set from high-throughput molecular dynamics simulation. The ML model's generalization ability on an unlabeled data set is especially focused, and the model's sensitivity to topology and the molecular weight of polymers is also taken into consideration. This benchmark study provides not only a guideline for the Tg prediction task but also a useful reference for other polymer informatics tasks.

Membranes for Cation Transport Based on Dendronized Poly(epichlorohydrin-co-ethylene oxide). Part 1: The Effect of Dendron Amount and Column Orientation on Copolymer Mobility.

Dendronized polyethers give rise to columnar LC structures which can successfully act as cation transport materials. Therefore, we prepared two different materials, based on Poly(epichlorohydrin-co-ethylene oxide) (PECH-co-EO) grafted with methyl 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy] benzoate, containing 20% or 40% modified units, respectively. The obtained polymers were characterized by differential scanning calorimetry (DSC), X-ray diffraction and optical microscopy between crossed polars (POM) and compared to the unmodified PECH-co-EO. In order to reach efficient transport properties, homeotropically oriented membranes were prepared by a fine-tuned thermal annealing treatment and were subsequently investigated by dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA). We found that the presence of the dendrons induces a main chain partial crystallization of the polyether chain and coherently increases the polymer Tg. This effect is more evident in the oriented membranes. As for copolymer orientation upon annealing, the cooling rate and the annealing temperature were the most crucial factors. DMTA and DETA confirmed that grafting with the dendron strongly hinders copolymer motions, but did not show great differences between unoriented and oriented membranes, regardless of the amount of dendrons.

Investigation into the role of the polymer in enhancing microwave-induced in situ amorphization

Microwave-induced in situ amorphization is an emerging technology to tackle the persistent stability issue of amorphous solid dispersions (ASDs) during manufacture and storage. The aim of this study was to introduce new effective polymeric carriers with diverse properties to microwave-induced in situ amorphization and to better understand their functions in relation to the final dissolution performance of microwaved tablets. Tablets composed of indomethacin (IND) and different polymers were compacted, stored at 75% relative humidity for at least 1 week and microwaved at 1000 W to induce amorphization. A series of polymers, polyvinylpyrrolidone/vinyl acetate copolymers (PVP/VA) of different monomer weight ratios displaying varyingproperties in functional groupratio, hygroscopicity, molecular weight (Mw), and glass transition temperature (Tg) of the polymer were used as model carriers. The results suggested that more than 90% of IND was amorphized after 20 mins microwaving in all 20% (w/w) drug loaded tablets except for IND:PVAc tablets presenting approx. 36% residual crystallinity. Among them, tablets composed of PVP/VA I-335 and PVP K30 achieved complete in situ amorphization upon microwaving. Further analysis indicated that the influencing factors, polymer Mw and Tg of moisture-plasticized polymer, played a major role in microwave-induced in situ amorphization. In in vitro dissolution study, ASDs containing PVP/VA I-535 with moderate hydrophilicity and 0.96 ± 1.92% IND residual crystallinity showed the most rapid and complete drug release among all formulations, presenting the most promising dissolution performance. Further study on the chemical stability of such formulation showed a statistically insignificant decrease of drug content after pre-conditioning and microwaving (P = 0.288 > 0.05).

Effect of side groups on glass transition temperatures of Poly(ethoxy/phenoxy)phosphazenes: Prediction and synthesis

Poly(aryloxyphosphazenes) are thermally stable, insulative, fire proof, and ablative resistant in extreme combustion, and can be applied as an insulated covering of high voltage cable and thermal shielding material for aircraft and spacecraft. However, being an elastomer, its higher glass transition temperature (Tg above −15 °C) limits the application in certain aspects. Therefore, adjustment of the Tg of poly(aryloxyphosphazenes) has become a research focus to improve overall performance. Introducing substituents such as alkoxy groups has been identified as an effective approach to lower the polymer Tg. In this study, based on the introduction of the different ratios of the ethoxy substituents in poly(bisphenoxyphosphazene), a series of simulations and experimental studies have been carried out for predicting the Tg of polyphosphazenes, along with establishing the relationships among synthesis, structure, and Tg. Molecular dynamics (MD) simulations using COMPASS force field and empirical Flory-Fox equation have been used to predict the Tg of the polymers and confirm the compatibility with the experimental data. Overall, the simulation results are noted to be in good agreement with the experimental values, and the Tg of the polymers gradually decreases with an increase in the ethoxy content. The proposed methods are efficient for the prediction of the Tg values of polyphosphazenes and can also be used for the structure prediction via the desired Tg, which is likely to have broad application for targeted polyphosphazenes synthesis.

Film formation of Alkali Soluble Resin (ASR) stabilized latexes

Alkali soluble resin (ASR) stabilized latexes are commonly employed in the development of waterborne coatings with good mechanical properties. However, despite their widespread use, little is known about how the nature of the hydroplasticized, high Tg ASR influences the film formation process and how systems can be designed to minimize the minimum film formation temperature (MFFT). In this work we synthesize a series of ASRs and ASR stabilized latexes in order to explore how the ASR influences the drying and deformation processes occurring during film formation. It is shown the ASR absorbs water and serves to increase the effective volume fraction of polymer during drying. Despite often being considered as an aqueous solution, the ASR behaves more like a conventional colloidal polymer and its film formation behavior is dictated by the wet Tg of the ASR. In ASR/latex blends both the wet Tg of the ASR and the Tg of the main emulsion polymer affects the MFFT. It is shown that high Tg ASRs (Tg > 100 °C) can be easily used in formulations that have MFFT <20 °C. In addition, for latexes with high Tg (Tg > 60 °C), using correct design strategies, hydroplasticized ASRs can be employed to lower the MFFT to below ambient temperature. These insights should allow for the effective development of latex films with low MFFT but mechanical properties more comparable to their solvent based counterparts.

Determination of glass transition temperature and application for fabrication of polyphosphazene with high performance

To determine the relations of performance and structure accurately, polyphosphazenes with various substitution rates of phenoxy and ethoxy were prepared by nucleophillic substitution reaction, their structures and glass transition temperature (Tg) were characterized by NMR and DSC, respectively, and theoretical Tg of polyphosphazenes containing various structural units were calculated by Fox equation. We can find that Tg of polyphosphazenes decreased with increase of ethoxy contents, which improved low temperature resistance of the polymer. According to the measured value and calculated value of Tg, as well as the deduced mathematical expression of Tailor-Gorden equation, the relationships between Tg and ethoxy contents were proposed, which demonstrated that a plot of the Tg vs. ethoxy contents yielded straight lines when polymer chain owned higher substitution rates of phenoxy or ethoxy, while Tg of polymers with more structural units of phenoxy and ethoxy would be adjusted by a parameter of ωB. Based on the proposed relation, the application of fabrication on polyaryloxyphosphazene elastomer with better mechanical properties and low temperature resistance was successfully carried out. Therefore, the proposed methods can be useful in the prediction of polymer Tg and can also be used for structure prediction of polymers to match a target Tg value by this means, which are likely to have broad applications in polymer science fields.

Predicting Polymers' Glass Transition Temperature by a Chemical Language Processing Model.

We propose a chemical language processing model to predict polymers’ glass transition temperature () through a polymer language (SMILES, Simplified Molecular Input Line Entry System) embedding and recurrent neural network. This model only receives the SMILES strings of a polymer’s repeat units as inputs and considers the SMILES strings as sequential data at the character level. Using this method, there is no need to calculate any additional molecular descriptors or fingerprints of polymers, and thereby, being very computationally efficient. More importantly, it avoids the difficulties to generate molecular descriptors for repeat units containing polymerization point ‘*’. Results show that the trained model demonstrates reasonable prediction performance on unseen polymer’s . Besides, this model is further applied for high-throughput screening on an unlabeled polymer database to identify high-temperature polymers that are desired for applications in extreme environments. Our work demonstrates that the SMILES strings of polymer repeat units can be used as an effective feature representation to develop a chemical language processing model for predictions of polymer . The framework of this model is general and can be used to construct structure–property relationships for other polymer properties.

Localized Deep and Shallow Traps of α-Peaks from Thermally Stimulated Current (TSC) Measurement on Thermoplastic Polymers

In this paper, trap levels around the glass transition temperature (Tg) of polymers have been characterized using Thermally Stimulated Current (TSC) technique. Deconvolution on α-peaks of the Tg for PE (-104 °C), plasticized PVC (-35 °C), PMMA (90 °C) and PET (96 °C) were carried out based on the first-order kinetic theory for non-Debye relaxation. Using temperature, T from TSC experimental data, we have successfully separated the α-peaks of the thermoplastic polymers. It is found that the complex curve of α-peaks can composed of four (4) to eight (8) sub peaks. Dominant sub peaks were identified at Tmax = -105 °C, -34 °C, 89 °C and 92 °C for PE, pPVC, PMMA and PET, respectively. These peaks show activation energy, Ea of shallow and deep trap centers ranged from 0.3 eV to 4.6 Ev where they represent the depolarization of localized dipoles and space charges relaxations in the polymers.