The Photopolymer Science and Technology Award No. 241100, the Outstanding Achievement Award 2024 was presented to Dr. Makoto Hanabata (Photofunctional Materials Research Co., Ltd.) for his outstanding achievements in photopolymer science and technology, “Pioneering Technology of the Novolak-Diazonaphthoquinone resist design for g-line(436nm) and i-line(365nm) photoresist platform and materials”.

The differences in casting solvents have a significant influence on the microphase-separated structures. We synthesized ABC/ACB-type linear triblock copolymers composed of polystyrene and polymethacrylate. To reveal the effects of casting solvents, we utilized tetrahydrofuran (THF) and chloroform. Regarding the swelling ratio of block segments, PS swelled the most when THF was used as the casting solvent. However, PS swelled the least when chloroform was used. Before thermal annealing of the bulk samples, a gyroid structure was obtained only with THF, while a lamellar structure was obtained only with chloroform.

Self-assembled double gyroid (DG) structures derived from block copolymers have garnered significant interest due to their broad potential for material development based on the characteristics of their nanostructural morphology. This study identified an efficient process to fabricate DG structures by employing ABC triblock terpolymers and solvent casting techniques. Poly(2,2,2-trifluoroethyl methacrylate (PTFEMA)-b-styrene (PS)-b-(4-vinyl pyridine) (P4VP), referred to as FSP triblock terpolymer, was successfully synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Films derived from a chloroform (CHCl₃) solution of this terpolymer were subsequently formed. The morphology in the films was characterized using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Structural analysis revealed that the CHCl₃ casting technique significantly expanded the DG region, with the volume fraction ratio of P4VP to PTFEMA (φ_P4VP/φ_PTFEMA) ranging from 0.34 to 1.70, as compared to the intrinsic range of 1.06 to 1.70. This wider composition range was attributed to the superior swelling ratio of the P4VP blocks when exposed to the CHCl₃ vapor among all components of the FSP triblock terpolymer. The utilization of solvent vapor annealing proved to be an effective strategy for the rational production of advanced DG structures.

Star-shaped ABC miktoarm terpolymers consisting of three different polymers are well-known to form a much richer variety of microphase-separated structures than linear AB-type diblock copolymers due to the addition of a third block. ABC-type block copolymers show promise in various applications, including multifunctional sensors, catalysts, separation membranes, and filters. Star-shaped miktoarm terpolymers have attracted significant attention because of their unique chemical structures, morphologies, and novel physical attributes that were never thought possible for linear polymers. However, star-shaped miktoarm terpolymers are synthetically challenging because combining different polymerization methods and multiple protection strategies are usually necessary to synthesize these polymers. Our research group, therefore, tried to synthesize star-shaped ABC miktoarm terpolymers in a one-pot two-step fashion by combining multicomponent reaction (MCR) and click reaction. To achieve this method, we considered the synthetic strategy of combining three different polymer arms. In this 'arm-first' approach, the star-shape miktoarm terpolymers composed of (PI)(PS)(PTFEMA) (PI: polyisoprene, PS: polystyrene, PTFEMA: poly(2,2,2-trifluoroethyl methacrylate)) are synthesized through an MCR involving CO₂, PI with an alkyne terminus, and PS with a bromo terminus, followed by a post-modification step where PTFEMA with an amino terminus is attached via an amino-yen click reaction.

To investigate the influence of functional groups on the interactions within segments of side-chain functionalized block copolymers (BCPs), a series of homopolymers was synthesized followed by post-functionalization. Specifically, polystyrene (PS), and poly(allyl glycidyl ether) (PAGE) were synthesized via anionic polymerization or catalyzed ring-opening polymerization respectively. Thiol-ene click chemistry was employed for the post-functionalization of alkyl, hydroxyl, and carboxyl groups in the resulting polymers. Subsequently, the Hansen solubility parameters (HSP) of homopolymers were estimated using a multi-solvent method. Initially, the HSP distance (Ra) between homopolymer PS and PAGE was 5.03. After the introduction of alkyl groups, the Ra between PS and PAGE(CH₃[100%]) decreased to 1.23. In contrast, the Ra between PS and PAGE(OH[100%]) or PAGE(COOH[100%]) increased to 10.20. These results showed a trend consistent with the effective Flory–Huggins interaction parameter (χ_eff) values which we measured in our previous work. This demonstrates the potential of HSP in elucidating and predicting the interactions between PS and PAGE.

Cesium lead chloride, CsPbCl₃, perovskite nanocrystals emitting pure blue colour at 405 nm were synthesized by employing oleylammonium chloride salt as an alternative halide source injected to a solution containing lead and cesium precursors with alkyl ligands. The synthetic parameters/conditions and purification method were modified to improve their photoluminescence quantum yields (PLQYs). PLQY was increased by increasing oleylammonium chloride concentration relative to lead ion concentration. PLQY of 60% was achieved by optimizing these parameters. The synthesized NCs indicated prolonged stability, i.e. maintaining the maximum PLQY for at least 8 days under ambient condition.

Green-light wavelength-selective organic solar cells (GLWS-OSCs) utilize green-light for energy conversion and transmitted red and blue light for crop growth, potentially addressing key challenges for the energy supply in the greenhouses. Towards scaling up GLWS-OSCs via environmentally friendly process, fabrication the active layer using non-halogenated solvent process is essential. Here, we investigated the combination of poly(3-hexylthiophene) (P3HT) as a donor with nonfullerene acceptors (FBR and FBRCN) to fabricate o-xylene-processed GLWS-OSCs. Absorption measurements of FBR and FBRCN reveal the high molar extinction coefficient and strong absorption bands in the green-light wavelength region of 500-600 nm. Due to the appropriate matching of the frontier molecular orbital energy levels of FBR and FBRCN with P3HT, the P3HT:FBR and P3HT:FBRCN films showed high green-light wavelength-selective factors as well as reasonable power conversion efficiencies in the green-light region in OSCs. Photosynthetic rate measurements using strawberry leaves demonstrated that the photosynthetic rate through the transmitted light of the P3HT:FBRCN film is higher than that of the P3HT:FBR film. These results demonstrate that development of nonfullerene acceptors applicable to green-solvent process is important research direction for realizing GLWS-OSCs in new greenhouse agrivoltaics.

Over the past decade, organic photovoltaics (OPVs) have improved significantly, largely due to a new type of component called non-fullerene acceptors (NFAs) with acceptor-donor-acceptor (A-D-A) type structures. In this study, we created three different NFAs, all of which have an anthracene-fused nonacyclic D core (ATTICs). Despite having the same end A groups and side chains, these three ATTICs exhibited different behaviors due to the variations in the nonacyclic D cores, i.e., the positions and carbon numbers of non-aromatic rings fused to anthracene. One of the ATTICs did not dissolve well enough to be used in an OPV. However, when we used the other two NFAs to fabricate the OPVs with a conjugated polymer donor J71, they exhibited power conversion efficiencies of 7.1% and 1.8%. This shows that even small changes to the design of the NFAs can have a large impact on the photovoltaic performance.

The degradation of modified polystyrenes having tertiary ether linkages or carbonate linkages were carried out by near infrared light (NIR) irradiation and subsequent heating. The polymer films containing a photoacid generator and a photon upconversion nanoparticle (UCNP) were decomposed to form isobutene and/or carbon dioxide by the NIR irradiation and subsequent heating. The thermal decomposition mechanism of the polymers assisted by NIR irradiation was investigated and discussed in terms of the irradiation and thermolysis conditions. Photolysis of the photoacid generator by NIR irradiation was investigated by UV-vis spectroscopy. We believe that the degradation by the NIR and subsequent heating contributes to the easy recycling of composite materials.

Degradation techniques of networked polymeric materials are highly desired from the viewpoint of recycling, repair, and reuse of thermosets. Covalent adaptable networks enable easier degradation through bond exchange, and oxime esters attract attention for their associative bond exchange between free oximes at milder condition without a catalyst. On the other hand, oxime esters are known to show high photoreactivity when chromophore units are involved. Herein we demonstrate thermal crosslinking of copolymers bearing oxime ester groups with a molecular multifunctional oxime and their decrosslinking on UV-irradiation in film state. As monomers bearing oxime ester units, acetone O-methacryloyloxime and cyclohexanone O-methacryloyloxime were copolymerized with styrene and methyl methacrylate. On baking at 180 ℃ in the presence of truxenone trioxime, these copolymer films became insoluble in chloroform. Furthermore, the baked films became soluble on irradiation with Hg-Xe lamp. These behaviors suggested the proceeding of thermal bond exchanges of oxime ester groups in side-chains and the photolysis of the resulting oxime ester linker units which became photoreactive with truxene chromophore. The effect of comonomers and substituents in oxime esters are discussed. Also, we could find the effect of photoirradiation on the thermal exchange by stripe pattern formation. These results showed the potential of oxime ester units as exchanging ability of covalent bonds which can be controlled by photoirradiation.

We prepared light-sensitive mixture systems consisting of both major azobenzene-containing components (linear amphiphile, AzEG, and block copolymer, pAzBu) and trigonal molecule (3Br) as a minor functional compound, in order to create a new type of functional organic materials capable of photoswitching of color, emission, and surface morphology. 3Br was chosen because it is red, aggregation-induced emission enhancement (AIE/AIEE)-active, and has a strong tendency to grow into crystalline one-dimensional (1D) fibers, allowing fluorescent nano- and microstructures formed as a result of assembly to be readily observed. First, we examined what shape of assembled aggregates 3Br produced in mixture systems with AzEG and pAzBu as major components. Investigations of how the spectroscopic (color and emission) characteristics of the resulting 3Br-based aggregates were affected by light-sensitive surrounding environments were followed. In 3Br-AzEG (1:18) THF-H₂O mixture suspensions, 3Br and amphiphilic AzEG molecules grew into red fluorescent microrods and nonfluorescent spherical objects, respectively. On the other hand, 3Br-pAzBu blend films exhibited a large amount of micrometer-sized 3Br rods. Importantly, a very short period of light irradiation resulted in noticeable changes in the color and emission intensity of the rods as well as the surface morphology of the blend films.

The reversible photoisomerization behaviors of p-hydroxyazobenzene derivative ((E)-4-((3,5-diethyl-4’-(hexyloxy)-[1,1’-biphenyl]-4-yl)diazenyl)phenol: C6AzOH) in a variety of solvents was investigated. The relatively less polar solvents such as tetrahydrofuran (THF), ethyl acetate, and toluene supported the generation of ~80-90% of the corresponding cis-isomer. Subsequent irradiation with visible light converted the cis-isomer to the original trans-isomer. By contrast, due to fast thermal cis-to-trans isomerization in relatively polar solvents (such as dimethyl sulfoxide (DMSO), N, N-dimethyl formamide (DMF), methanol (MeOH), and dichloromethane), UV-induced trans-to-cis isomerization could not be observed using UV-visible absorption and ¹H NMR spectroscopic measurements. Bubble-like aggregates produced in a THF-H₂O turbid suspension had crystalline structures and exhibited little light-response according to different wavelengths of light.

UV-curable coatings have attracted the interest of researchers in industry and academia because of their outstanding features. In this paper, the effect of monomer functionality and monomer concentration on the photo-induced nano-gelation of UV-curable coatings has been investigated. The coatings were prepared by incorporating an aliphatic urethane acrylate oligomer with a mono-functional monomer (phenoxy ethyl acrylate (PEA)) or multifunctional acrylate monomers (1,6-hexanediol diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA)) to form different nano-gel domains. The viscoelastic properties of the coatings, including crosslinking density, glass transition temperature, and elastic modulus, were evaluated using dynamic mechanical thermal analysis (DMTA). The surface hardness of the applied coatings was measured by two different methods: the pendulum hardness test and Knoop micro-indentation. Surface roughness and dimensions of nano-gels were evaluated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed the effect of nano-gel dimensions on the mechanical properties of coatings. The surface hardness of the coatings obtained by different methods showed the same results. The findings of this study provide important insights into the design and optimization of UV-solidified coatings for applications in the field of automotive coatings.

Although the diagnostic utility of interstitial fluid (ISF) has been extensively explored, collecting and sensing ISF in the body remains challenging. Microneedle devices offer a promising approach for minimally invasive methods to obtain ISF with a small volume or to sense biomolecules in the ISF within the body. In this study, we developed a microneedle with a small volume hydrogel block at the needle tip. The hydrogel block was formed through a photopolymerization reaction of polyethylene glycol diacrylate (PEGDA) under 365 nm irradiation. The hydrogel block measured 100 µm in diameter and 100 µm in length, with a total volume of 0.79 nL. The fabricated microneedle had a high-aspect ratio shape (500 µm in base diameter, 200 µm in top diameter, and 2000 µm in length), reaching the reticular layer containing blood vessels. Therefore, microneedle devices can be utilized to obtain ISF with a small volume and to sense biomolecules within the body.

Polymer alloys, formed by blending biodegradable and conductive polymers, offer properties challenging to achieve with a single material, thus garnering significant attention. Among these, Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS), a biocompatible conductive polymer composed of PEDOT doped with PSS, has been extensively researched due to its electrochemical, thermal, and oxidative stability, paving the way for practical applications. In this study, we delve into the preparation process of polymer alloy films comprising PEDOT:PSS and poly(L-lactic acid) (PLLA), a biodegradable polymer. We explore the compatibility of immiscible polymer blends by mixing a PLLA solution in either 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) or dimethyl sulfoxide (DMSO) with a PEDOT:PSS aqueous dispersion. Using a solvent mixture of HFIP and water resulted in separate phase domains of PLLA and PEDOT:PSS, failing to form a cohesive film. However, employing a DMSO and water solvent mixture yielded films with uniformly dispersed PLLA and PEDOT:PSS phases at a microscopic level. We conducted numerical thermodynamic simulations based on Hansen Solubility Parameters (HSP) to elucidate the experimental results and examine the impact of solubility changes during solvent evaporation on polymer precipitation. Our findings demonstrate the feasibility of fabricating alloy films with uniformly dispersed constituent polymer phases by selecting solvents with comparable solubilities for both polymers.