24 research outputs found
Representing Polymers as Periodic Graphs with Learned Descriptors for Accurate Polymer Property Predictions
One of the grand challenges of utilizing machine learning for the discovery
of innovative new polymers lies in the difficulty of accurately representing
the complex structures of polymeric materials. Although a wide array of
hand-designed polymer representations have been explored, there has yet to be
an ideal solution for how to capture the periodicity of polymer structures, and
how to develop polymer descriptors without the need for human feature design.
In this work, we tackle these problems through the development of our periodic
polymer graph representation. Our pipeline for polymer property predictions is
comprised of our polymer graph representation that naturally accounts for the
periodicity of polymers, followed by a message-passing neural network (MPNN)
that leverages the power of graph deep learning to automatically learn
chemically-relevant polymer descriptors. Across a diverse dataset of 10 polymer
properties, we find that this polymer graph representation consistently
outperforms hand-designed representations with a 20% average reduction in
prediction error. Our results illustrate how the incorporation of chemical
intuition through directly encoding periodicity into our polymer graph
representation leads to a considerable improvement in the accuracy and
reliability of polymer property predictions. We also demonstrate how combining
polymer graph representations with message-passing neural network architectures
can automatically extract meaningful polymer features that are consistent with
human intuition, while outperforming human-derived features. This work
highlights the advancement in predictive capability that is possible if using
chemical descriptors that are specifically optimized for capturing the unique
chemical structure of polymers
Isoindigo-Containing Molecular Semiconductors: Effect of Backbone Extension on Molecular Organization and Organic Solar Cell Performance
We
have synthesized three new isoindigo-based small molecules by
extending the conjugated length through the incorporation of octyl-thiophene
units between the isoindigo core and benzothiophene terminal units.
Both UV–vis and Grazing incidence X-ray diffraction experiments
show that such extension of the π-conjugated backbone can induce
H-aggregation, and enhance crystallinity and molecular ordering of
these isoindigo-based small molecules in the solid state. Compared
to two other isoindigo-based derivatives in the series, the derivative
with two octyl-thiophene units, BT-T2-ID, is the most crystalline
and ordered, and its molecular packing motif appears to be substantially
different. Devices utilizing these new extended isoindigo-based small
molecules as the electron donor exhibit higher performance than those
utilizing nonextended BT-ID as the electron donor. Particularly, devices
containing BT-T2-ID in an as-cast blend with PC<sub>61</sub>BM show
power conversion efficiencies up to 3.4%, which is comparable to the
best devices containing isoindigo-based molecular semiconductors and
is a record among devices containing isoindigo-based small molecules
that were processed in the absence of any additives
Data-driven materials research enabled by natural language processing and information extraction
© 2020 Author(s). Given the emergence of data science and machine learning throughout all aspects of society, but particularly in the scientific domain, there is increased importance placed on obtaining data. Data in materials science are particularly heterogeneous, based on the significant range in materials classes that are explored and the variety of materials properties that are of interest. This leads to data that range many orders of magnitude, and these data may manifest as numerical text or image-based information, which requires quantitative interpretation. The ability to automatically consume and codify the scientific literature across domains - enabled by techniques adapted from the field of natural language processing - therefore has immense potential to unlock and generate the rich datasets necessary for data science and machine learning. This review focuses on the progress and practices of natural language processing and text mining of materials science literature and highlights opportunities for extracting additional information beyond text contained in figures and tables in articles. We discuss and provide examples for several reasons for the pursuit of natural language processing for materials, including data compilation, hypothesis development, and understanding the trends within and across fields. Current and emerging natural language processing methods along with their applications to materials science are detailed. We, then, discuss natural language processing and data challenges within the materials science domain where future directions may prove valuable
Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies
Structure–Property Relationship Study of Substitution Effects on Isoindigo-Based Model Compounds as Electron Donors in Organic Solar Cells
We designed and synthesized a series
of isoindigo-based derivatives to investigate how chemical structure
modification at both the 6,6′<i>-</i> and 5,5′-positions
of the core with electron-rich and electron-poor moieties affect photophysical
and redox properties as well as their solid-state organization. Our
studies reveal that 6,6′-substitution on the isoindigo core
results in a stronger intramolecular charge transfer band due to strong
electronic coupling between the 6,6′-substituent and the core,
whereas 5,5′-substitution induces a weaker CT band that is
more sensitive to the electronic nature of the substituents. In the
solid state, 6,6′-derivatives generally form <i>J</i>-aggregates, whereas 5,5′-derivatives form <i>H</i>-aggregates. With only two branched ethylhexyl side chains, the 6,6′-derivatives
form organized lamellar structures in the solid state. The incorporation
of electron-rich benzothiophene, <b>BT</b>, substituents further
enhances ordering, likely because of strong intermolecular donor–acceptor
interactions between the <b>BT</b> substituent and the electron-poor
isoindigo core on neighboring compounds. Collectively, the enhanced
photophysical properties and solid-state organization of the 6,6′-benzothiophene
substituted isoindigo derivative compared to the other isoindigo derivatives
examined in this study resulted in solar cells with higher power conversion
efficiencies when blended with a fullerene derivative
Data Mining for Parameters Affecting Polymorph Selection in Contorted Hexabenzocoronene Derivatives
The
macroscopic properties of molecular materials can be drastically
influenced by their solid-state packing arrangements, of which there
can be many (e.g., polymorphism). Strategies to controllably and predictively
access select polymorphs are thus highly desired, but computationally
predicting the conditions necessary to access a given polymorph is
challenging with the current state of the art. Using derivatives of
contorted hexabenzocoronene, cHBC, we employed data mining, rather
than first-principles approaches, to find relationships between the
crystallizing molecule, postdeposition solvent-vapor annealing conditions
that induce polymorphic transformation, and the resulting polymorphs.
This analysis yields a correlative function that can be used to successfully
predict the appearance of either one of two polymorphs in thin films
of cHBC derivatives. Within the postdeposition processing phase space
of cHBC derivatives, we have demonstrated an approach to generate
guidelines to select crystallization conditions to bias polymorph
access. We believe this approach can be applied more broadly to accelerate
the predictions of processing conditions to access desired molecular
polymorphs, making progress toward one of the grand challenges identified
by the Materials Genome Initiative
Data Mining for Parameters Affecting Polymorph Selection in Contorted Hexabenzocoronene Derivatives
The
macroscopic properties of molecular materials can be drastically
influenced by their solid-state packing arrangements, of which there
can be many (e.g., polymorphism). Strategies to controllably and predictively
access select polymorphs are thus highly desired, but computationally
predicting the conditions necessary to access a given polymorph is
challenging with the current state of the art. Using derivatives of
contorted hexabenzocoronene, cHBC, we employed data mining, rather
than first-principles approaches, to find relationships between the
crystallizing molecule, postdeposition solvent-vapor annealing conditions
that induce polymorphic transformation, and the resulting polymorphs.
This analysis yields a correlative function that can be used to successfully
predict the appearance of either one of two polymorphs in thin films
of cHBC derivatives. Within the postdeposition processing phase space
of cHBC derivatives, we have demonstrated an approach to generate
guidelines to select crystallization conditions to bias polymorph
access. We believe this approach can be applied more broadly to accelerate
the predictions of processing conditions to access desired molecular
polymorphs, making progress toward one of the grand challenges identified
by the Materials Genome Initiative