Styrene radical polymerization was carried out in the presence of a polymerizable dithioester, benzyl 4-vinyldithiobenzoate, which possesses a dithioester group and a polymerizable double bond. Branched polystyrene was formed during the polymerization, as indicated by multimodal GPC curves of the products. The branched polystyrene contains a dithiobenzoate C(dS)S moiety at each branch point and thus can be analyzed by cleavage with amine. After cleavage, the GPC profiles became narrow. The molecular weight of the cleaved product increased linearly with monomer conversion, illustrating a living fashion of the polymerization. Solution property obtained by simultaneous online measurements of viscosity and light scattering indicates that the viscosity of the branched product decreased remarkably as compared to the linear polystyrene of equivalent molecular weight. The copolymerization behavior of styrene and benzyl 4-vinyldithiobenzoate was investigated by FT-IR monitoring during the polymerization. The results show that the latter was incorporated homogeneously into polystyrene chain. Therefore, branched polystyrene was synthesized with controlled architecture in the light of the length and narrow distribution of primary chains as well as the degree and the distribution of branching along the polymer chain.

The field of machine learning is witnessing its golden era as deep learning slowly becomes the leader in this domain. Deep learning uses multiple layers to represent the abstractions of data to build computational models. Some key enabler deep learning algorithms such as generative adversarial networks, convolutional neural networks, and model transfers have completely changed our perception of information processing. However, there exists an aperture of understanding behind this tremendously fast-paced domain, because it was never previously represented from a multiscope perspective. The lack of core understanding renders these powerful methods as black-box machines that inhibit development at a fundamental level. Moreover, deep learning has repeatedly been perceived as a silver bullet to all stumbling blocks in machine learning, which is far from the truth. This article presents a comprehensive review of historical and recent state-of-the-art approaches in visual, audio, and text processing; social network analysis; and natural language processing, followed by the in-depth analysis on pivoting and groundbreaking advances in deep learning applications. It was also undertaken to review the issues faced in deep learning such as unsupervised learning, black-box models, and online learning and to illustrate how these challenges can be transformed into prolific future research avenues.

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Magnetic field alignment of rod-coil block copolymers is shown to proceed through coupling to the diamagnetic moment of individual rod blocks. Block copolymer self-assembly then leads to alignment of the interfaces perpendicular to the field lines and long range order on a 10 nm lengthscale. This is in contrast to previously demonstrated alignment techniques, which couple to the block copolymer interfaces rather than individual molecules. Furthermore, alignment occurs without direct physical contact to samples millimeters in size.

The lateral order of poly(styrene-block-isoprene) copolymer (PS-b-PI) thin films is characterized by the emerging technique of resonant soft X-ray scattering (RSOXS) at the carbon K edge and compared to ordering in bulk samples of the same materials measured using hard Xray small-angle scattering. We show using theory and experiment that the loss of scattering intensity expected with a decrease in sample volume can be overcome by tuning X-rays to the π* resonance of PS or PI. Using RSOXS, we study the microphase ordering of cylinder and sphere forming PS-b-PI thin films and compare these results to position space data obtained by atomic force microscopy. Our ability to examine large sample areas (~9000 µm 2 ) by RSOXS enables unambiguous identification of the lateral lattice structure in the thin films. In the case of the sphere forming copolymer thin film, where the spheres are hexagonally arranged, the average sphere-to-sphere spacing is between the bulk (body centered cubic) nearest neighbor and bulk unit cell spacings. In the case of the cylinder forming copolymer thin film, the cylinder-tocylinder spacing is within experimental error of that obtained in the bulk.3

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The formation of alternating electron transporting and hole transporting 15 nm lamellae within the active layer of an organic light-emitting diode (OLED) is demonstrated to improve device performance. A new multifunctional bipolar rod-coil block copolymer containing a poly(alkoxy phenylenevinylene) (PPV) rodshaped block as the hole transporting and emitting material and a poly(vinyloxadiazole) coil-shaped electron transporting block is synthesized. This new block copolymer is the active material of a self-assembling multicomponent electroluminescent device that can be deposited in a single step. In the thin film, grazing incidence X-ray scattering and transmission electron microscopy demonstrate that the layers form grains which are oriented bimodally: parallel and perpendicular from the anode. In this mixed orientation, the device demonstrates better performance than those with either pure PPV or a blend of the two analogous homopolymers as the active materials, i.e., higher external quantum efficiency (EQE) and brightness. This improved device performance is mainly attributed to the bipolar functionality and microphase separation of the block copolymer, which provide highly efficient hole and electron recombination at the nanodomain interfaces.

Branched polystyrene was synthesized through controlled radical polymerization of styrene in the presence of 4-(4′-vinylphenylmethoxy)-2,2,6,6-tetramethyl-1-piperidinyloxy (STEMPO) which possesses a nitroxyl stable radical and a polymerizable vinyl group. During the polymerization, STEMPO played the role of branching agent since it can polymerize as well as trap the propagating radical. The resulting polymer contained a labile covalent C-ON bond at each branch point and had broad molecular weight distribution. After being heated with phenylhydrazine, the GPC profile of the product became narrower due to cleavage of the branch points. The molecular weight of the cleaved product was proportional to monomer conversion, demonstrating a controlled growth of primary chains. 1 H NMR showed that, in the polymerization of deuterated styrene, the signal intensity of vinyl groups in STEMPO decreased at a constant rate with increasing monomer conversion. ESR measurement illustrated that the labile C-ON bonds at branch points were subject to thermal homolysis. The branched product was used as a macroinitiator for radical polymerization of 4-methoxystyrene. The resulting copolymer possessed a branched architecture of diblock primary chains with controlled length and narrow distribution.