Scanning Microscopic Light Scattering Research Articles

(Invited) Scanning Microscopic Light Scattering with Machine Learning for Quality Assurance of 3D-Printed Hydrogels

Scanning microscopic light scattering (SMILS) is a powerful tool for the characterization of soft and wet matter, including polymer gels, polymer solutions, and the dispersion of nanometer particles. Specially the SMILS has a special advantage to overcome the inhomogenities of the soft and wet matter. For example, the network structure of polymer gels is so stable that the inhomogenities due to the fluctuation under the formation of chemical reaction, i.e. gelation, tends to be fixed in the network structure. This kind of the static inhomogeneites causes the position dependence of the observation of the polymer gels in the experiment of light scattering. The SMILS is able to scan the sample of the soft and wet matter and observes many data in different positions in the same sample to obtain the space-averaged data of the time-averaged correlation functions of scattered photons. Then the SMILS determine the ensemble-averaged correlation function.However, through the actual experiences of the SMILS experiments, we knew that the set of many data in different positions has several bad data due to dust, stray light, and mechanical vibration. By thinning the set of data to remove the bad data, the net result of the ensemble-averaged correlation function tends to improve very well. In the previous studies, we sometimes obtained the 30-100 data in different positions and thinned out the data to remove the 1-70% based on the judgement of the observer. There is a problem that the thinned data may depend on the observer.To overcome this problem, we tried to apply machine learning for the SMILS experiments. In the machine-learning procedure, artificial intelligence was made to learn the thinning operation of the observer as a teacher so that the same thinning operation as the observer could be performed. The below-shown figure shows one of the results of this procedure. It is shown that the raw ensemble-averaged correlation function has the ambiguous four peaks of relaxation modes. However the thinned correlation function by the machine-learning procedure will improve and show only one nice-seeming peak. We will exam the reliability of this novel automation procedure especially for the 3D-printed hydrogel samples and will establish the novel AI-aimed SMILS system to be applied for quality assurance of 3D-printed hydrogels in near future. Figure 1

(Invited) Structural Analysis of Multifunctional Ionic Gels

Ionic liquid (IL) mediated gels commonly known as ion gels or ionic gels have received remarkable attention for their advanced application in electrochemical and electromechanical devices, such as actuators, lithium batteries, electric double-layer capacitors, dye-sensitized solar cells and fuel cells. In this work we focused to determine structural properties of thiol-ene crosslinked gels both in organic solvent dimethyl sulfoxide (DMSO) and IL, 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide (BMIm FSI) combining multifunctional thiol end-crosslinkers and diacrylate monomer via thiol-ene click reaction. We investigated their mechanical properties and internal structure by estimating mesh chain densities calculated from Young’s modulus compression test and nondestructive scattering method of determining mesh size by scanning microscopic light scattering (SMILS) techniques respectively. The mesh densities of the gels were found to be highly dependent on the functionality of the thiol compound both in IL and conventional solvent, DMSO. Finally, we compared the mesh chain densities determined by the two methods and discussed the assumptions to understand the internal structure of these gels.

Analysis of Internal Structural of 3D Printed Shape Memory Gels

Understanding the internal structure of the gels is important to comprehend their physico-chemical properties and propose better utilization in practical application. The scanning microscopic light scattering (SMILS) is one of the powerful tools to nondestructively characterize the internal structure of gels. The SMILS is a typical dynamic light scattering (DLS) system, which can be used to characterize the internal structure of gels by observing the diffusion process [1]. In our previous study we studied internal structures of Poly (N-N-dimethylacrylamide (PDMAAm) gels and different inter-crosslinking network (ICN) gels and compared their crosslinking density with ionic gels [2]. We also determined the soft to hard transition temperature of PDMAAm-co Stearyl acrylate (SA) shape memory gels SMGs prepared by mold techniques by carrying out temperature dependent SMILS measurements [3]. In this work, we present the structural analysis of 3D printed transparent SMGs containing two different hydrophobic crystalline monomers SA and Lauryl acrylate (LA) fabricated by optical stereolithography technique. By SMILS we can obtain a time- and space-averaged correlation function i.e., an ensemble-averaged correlation function to overcome the inhomogeneous media. For each sample, the time-averaged homodyne correlation functions g(2)(q,τ) were determined at several points, where q is scattering vector and τ is correlation time. Then the ensemble-averaged correlation function g(1)(q,τ) was calculated. Thus, the characteristic size of diffusing objects (mesh size) ξ can be estimated from the Einstein-Stokes formula. In the measurement of the SMGs, we controlled the angle of PMT and relaxation time distribution was calculated for every angle. We have correlated their internal structures with mechanical properties to understand their internal structures and made justified assumption on their structural homogeneities. H., Horie, K., Nozaki, R., Okada, M. Phys Rev E 68:031406-1-14 (2003)Ahmed, K., Watanabe, Y., Higashihara, T. Arafune, H. Kamijo, T., Morinaga, T. Sato, T., Makino, M. Kawakami, M., Furukawa, H. Microsyst Technol., 22, 17 (2016)Kabir, M., H., Gong, J., Watanabe, Y., Makino, M., Furukawa, H. Lett., 108, 239–242 (2013)

(Invited) Structural Analysis of Multifunctional Ionic Gels

Ionic liquied mediated gels commonly known as ion gels or ionic gels have received remarkable attention for their advanced application in electrochemical and electromechanical devices, such as actuators, lithium batteries, electric double-layer capacitors, dye-sensitized solar cells and fuel cells [1, 2]. Investigation of the internal structure of ionic gels have been previously reported by our research group to understand their network homogeneity in association with mechanical characterization[3]. In this work we focused to determine structural analysis of ionic gels combining multifunctional thiol monomers and IL 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide (BMImFSI). Therefore, we developed thiol monomer-based ionic gels via thiol-ene click reaction with theoretically homogeneous uniform network and investigated their mechanical properties using both conventional destructive method i.e. compression test and a unique nondestructive method using mesh size by scanning microscopic light scattering (SMILS) techniques [4]. The mesh size of the IGs was found to be highly dependent on the functionality of the monomer both in IL and conventional solvent media. Also long chain crosslinkers have been found to form dangling chain within the network hindering their homogeneous network formation. Thus our systems can offer to combine internal structures with the mechanical properties for characterization of soft materials in smart nondestructive ways.

3D Printable Particle-Type Double Network Gels Studied with Scanning Microscopic Light Scattering

We are conducting research on fine particle preparation double network gel (P-DN gel) which can be applied to 3D printer technology and is capable of high-intensity three-dimensional freeforming. Like the double network gel, the P-DN gels is composed of monomers having two different structures, a hard and brittle mesh structure (1st gel) and a flexible and extensible network structure (2nd gel). In our previous studies, the structure of the P-DN gels has been investigated with a scanning microscopic light scattering device. In this study, we attempted to improve the accuracy of measurement by adding latex particles to the P-DN gels. As a result, the intensity of the scattered light was emphasized compared with ordinary P-DN.

Physical Properties of Hydrogel Objects By 3D-Printing

Since the gel has soft physical properties, it was difficult to process by conventional cutting or casting, but 3D gel printer was developed, and three-dimensional free modeling of the gel became possible. In this study, it is presented that the relationship between printing parameters of a 3D gel printer "Soft and Wet Intelligent Matter-Easy Realizer (SWIM-ER)" and mechanical properties of the fabricated gel objects by SWIM-ER. The printer can fabricate hydrogel objects by scanning of ultra-violet (UV) light irradiation (photopolymerization). Various hydrogels objects were printed with different scanning velocity of UV light. We measured the water content and mesh sizes of gel objects utilizing Scanning Microscopic Light Scattering (SMILS). Furthermore, we also printed the gel objects with multiple scan rates with constant UV light irradiation energy, and measured sizes of gel objects, and performed the compression test. It was observed that the physical properties of printed hydrogel objects are strongly related with 3D printing parameters due to difference in crosslinking density of polymer network.[1] Ref. [1] Takafumi Ota, et al., Mechanical Engineering Journal, 5, 1, 17-00538 (2018).

Improve the accuracy of 3D gel printer by incorporating Scanning Microscopic Light Scattering System

Improve the accuracy of 3D gel printer by incorporating Scanning Microscopic Light Scattering System

Synthesis of organic‐inorganic hybrid gels by means of thiol‐ene and azide‐alkene reactions

ABSTRACTOrganic–inorganic hybrid gels have been synthesized from a multi‐vinyl functional cyclic siloxane, 1,3,5,7‐tetravinyltetramethylcyclotetrasiloxane (TVMCTS), or a cubic silsesquioxane, octavinyloctasilasesquioxane (PVOSS), and α,ω‐dithiol compounds, 1,6‐hexanedithiol (HDT), 1,10‐decanedithiol (DDT), using thiol‐ene reaction in toluene. The network structure of the resulting gels, mesh size and mesh size distribution, was quantitatively characterized by means of a scanning microscopic light scattering (SMILS). The gels obtained from TVMCTS‐HDT formed homogeneous network structure with 1.5–1.6 nm mesh. Relaxation peaks derived from large clusters and/or micro gels were detected in the SMILS analysis of the TVMCTS‐DDT, PVOSS‐HDT, and PVOSS‐DDT gels besides those from the small meshes. The organic–inorganic hybrid gels were also synthesized from TVMCTS, PVOSS with α,ω‐diazide compounds, 1,6‐hexanediazide (HDA), 1,10‐decanediazide (DDA), using azide‐alkene reaction in toluene. All the gels obtained with the azide‐alkene reaction formed the homogeneous network structure. Enthalpy relaxation at the glass transition of the dried samples was detected by differential scanning calorimetry to study the network uniformity of the original gels. The gels synthesized by the azide‐alkene reaction showed larger enthalpy than the gels synthesized by the thiol‐ene reaction, indicating homogeneous network structure in the former gels. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2229–2238

Synthesis and Structure of Organic-Inorganic Hybrid Semi-interpenetrating Polymer Network Gels

Semi-interpenetrating polymer network (semi-IPN) gels have been synthesized using a hydrosilylation reaction of 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) as a joint molecule, and a,w-nonconjugated dienes, 1,5-hexadiene (HD) or 1,9-decadiene (DD) as linker molecules in the presence of polystyrene (PS) as a liner polymers in toluene or cyclohexane. Network structure, mesh size and mesh size distribution, of the resulting semi-IPN gels was quantitatively characterized by means of a scanning microscopic light scattering (SMILS). The relaxation peaks derived from three kinds of structures were detected in the semi-IPN gels prepared in toluene by the SMILS analysis. One was derived from the mesh formed by TMCTS/a,w-nonconjugated dienes about 1-2 nm. Others were derived from transition networks about 20-150 nm and large clustered liner polymer chains about 700-2300 nm. Effect of concentration and molecular weight of the liner polymer on the network structure of the semi-IPN gels in toluene was investigated. The relaxation peaks derived from transition networks or random coils formed by aggregated PS chains were detected in the semi-IPN gels containing high concentration or high molecular weight PS. The semi-IPN gels containing PS were also prepared in cyclohexane as a poor solvent for PS at 40ºC, which was a higher temperature than the upper critical solution temperature (UCST = 34ºC) of PS in cyclohexane. The network structure of the semi-IPN gels was traced by SMILS on the cooling process. In the semi-IPN gel with the short linker molecule of HD, the relaxation peak derived from clustered PS chains was detected over the UCST. By contrast, the relaxation peak derived from transition network was observed in the semi-IPN gel with the long linker molecule of DD.

走査型顕微光散乱装置による吸水性高分子ゲルの内部構造解析

走査型顕微光散乱装置(Scanning Microscopic Light Scattering：通称SMILS)によって，代表的な吸水性高分子ゲルであるポリアクリル酸ナトリウム(PSA)ゲル，PSAゲルを酸型にしたポリアクリル酸(PAA)ゲルの内部構造評価を行った．SMILSによって得られる動的ゆらぎの緩和時間分布関数を基準に膨潤率・ヤング率を併用し，ゲルの内部構造を評価した．とくに，動的ゆらぎから得られるスケールをFluctuation Size (FS)とし，FSから算出される架橋密度(νS)，膨潤率から算出される架橋密度(νW)，ヤング率から算出される架橋密度(νY)を比較することにより，総合的にゲル内部の網目構造を評価した．PSAゲルにおいては，νW ，νY に対してνSは非常に大きな値となったため，SMILSで測定されるFSの値はゲルの網目サイズを直接示唆していない可能性がわかった．さらに，PSAゲルではνY>νWとなり，さらに，被吸収液の塩濃度が低くなるにつれてその差が大きくなることから，ネットワーク主鎖上のイオン基どうしの静電反発が増えるほど主鎖の剛直性が増していることが明らかになった．また，それに伴ってνSが増大する事から，今回の動的光散乱測定においてもネットワーク主鎖の剛直性がνSに影響を及ぼしていることが推察された．そのため，PSAゲルの内部構造を動的光散乱によって解析する場合には，FSの減少を考慮した適切な補正手法が必要になることが判明した．

Structure and formation processes of syndiotactic-polystyrene or styrene-based copolymer-organic solvent gels studied using scanning microscopic light scattering

The network structure of syndiotactic-polystyrene (sPS)- or syndiotactic-poly(styrene-co-4-R-styrene)-organic solvent gels has been quantitatively studied by means of scanning microscopic light scattering (SMILS). SMILS analysis indicated that sPS gels prepared in chloroform, benzene, toluene, and o-dichlorobenzene (ODCB) formed network structures with small mesh sizes, ~0.6–1.8 nm, and large cluster structures, ~1000–6000 nm. The cluster size in the gels increased with increasing sPS concentration. The mesh and cluster sizes of sPS gels prepared in ODCB was the smallest among the used solvents owing to its high viscosity. Gelation of the St/CH3St (MeSt)-toluene system at high temperatures induced slow gel formation and made it possible to trace the time evolution of the network structure by SMILS. tert-C4H9St (BuSt) units in St/BuSt drastically decreased the gel formation rate, and the formation process of the St/BuSt-toluene system could be traced by SMILS and FT-IR spectroscopy at room temperature. The results indicated growth of the cluster structure during gelation. St/4-hydroxystyrene formed gels in dioxane. A gel of an St copolymer containing an anthracene (An) group was prepared in toluene, and photodimerization of the An groups was induced by UV irradiation accompanied by formation of the large cluster structure. Network structure of syndiotactic-polystyrene (sPS) or syndiotactic-poly(styrene-co-4-R-styrene) (St/RSt) -organic solvents gels has been quantitatively studied by means of a scanning microscopic light scattering (SMILS). The SMILS analysis cleared that most of the gels showed relaxation peaks derived from small mesh size ~0.6–1.8 nm and large cluster structure ~1000–6000 nm, and a gel formation model was proposed based on the analysis. Interaction between R groups (R=OH, antracenecarbonyl) affected the network structure of the gels.

Structural Analysis of Shape Memory Gel

The determination of structural properties of a material is important before its practical application. The analysis data provide us some information whether the material is suitable for application or not. The prospective applications of soft and wet materials explore the new era in the material science as an industrial material especially for medical applications. Shape memory gels (SMGs) are one kind of unique soft and wet materials having shape recovery property which is suitable for medical application such as bandages for broken bones or making optical lens and so on. In the present study, scanning microscopic light scattering (SMILS) is used to characterize the internal structure of shape memory gels. It is observed that the SMGs are transparent at room temperature, mechanically elastic and ductile as well as thermoresponsive despite the high water contents. We confirm the mesh size in nanometer scale of the internal network structure and the critical behavior of the SMG by dynamic light scattering (DLS). The mechanical properties also have been characterized by dynamic mechanical analysis (DMA).

J044021 硝子体非破壊診断システムの開発([J044-02]ソフトマター・イノベーション(2))

Eyeball plays a quite important role in acquiring vision. Vitreous body occupies the largest part in the eyeball and consists of biological, elastic, transparent, gel materials. In the present medical examination, the non-destructive examination method of the vitreous body has not been established. Here we focus on an application of dynamic light scattering to this topic. We try to apply our lab-made apparatus, scanning microscopic light scattering (SMILS), which was specially designed for observing the nanometer-scale network structure in gel materials. Also we try to implement the SMILS technology to a commercial apparatus, nano Partica (Horiba Co., Ltd.), in order to examine the vitreous body. We add several customizations to the nano-Partica. By using both the SMILS and the customized nano Partica, we successfully examined the vitreous bodies from patients and healthy pigs. This work is kindly supported by the doctors in the Hospital of Yamagata University.

205 可視化走査型顕微光散乱(Visual-SMILS)によるゲル機械材料の動的揺らぎの可視化解析

205 可視化走査型顕微光散乱(Visual-SMILS)によるゲル機械材料の動的揺らぎの可視化解析

Polymer Effects on Turbulence in Flowing Soap Films Studied with Film Interference Flow Imaging Method

Thin liquid layer exists between bone and bone in joint of human body, and also, thin tear film covers cornea. These thin liquid layers contain biopolymer such as hyaluronic acid and mucin. These thin liquids make it possible that smooth movement of the joints and smooth blinks. In this research, effects of polymer in thin liquid layer are studied by using flowing soap films. Soap films consist of about 4 &microm thickness water layer inside and surfactant mono-layer in the surface. Interference patterns of the soap films are affected by the thickness of the water layer. Thus the interference pattern reflects the behavior of the water layer. In this study, turbulence was made in flowing soap films, the effects of long flexible polymer Polyethylene oxide (PEO, Mw=4x106) to the turbulence was observed by the interference pattern. This technique is proposed as Film Interference Flow Imaging method (FIFI). Thickness and velocity information of the turbulence were observed by FIFI. Inner structure of the soap solution containing PEO was observed by Scanning Microscopic Light Scattering (SMILS) which is a light scattering system specialized for analyzing microscopic structures. For some applications, investigations of the polymer effects in thin liquid layer are useful for the development of polymer drag for joint pain or dry eyes.

181 走査型顕微光散乱(SMILS)によるソフト&ウェット材料の構造解析と力学物性(技術と社会/バイオエンジニアリングI,一般講演)

181 走査型顕微光散乱(SMILS)によるソフト&ウェット材料の構造解析と力学物性(技術と社会/バイオエンジニアリングI,一般講演)

408 走査型顕微光散乱(SMILS)によるゲルの網目構造解析システムの開発(材料・設計(2))

408 走査型顕微光散乱(SMILS)によるゲルの網目構造解析システムの開発(材料・設計(2))

Synthesis of Organic−Inorganic Hybrid Gels from Siloxane or Silsesquioxane and α,ω-Nonconjugated Dienes by Means of a Photo Hydrosilylation Reaction

Organic−inorganic hybrid gels have been synthesized from the multifunctional cyclic siloxane, 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), or the cubic silsesquioxane, 1,3,5,7,9,11,13,15-octakis(dimethylsilyloxy)pentacyclo-[9,5,1,1,1,1]octasilsesquioxane (POSS), as cross-linking reagents with α,ω-nonconjugated dienes, 1,5-hexadiene (HD) or 1,9-decadiene (DD), using a photo hydrosilylation reaction with a bis(acetylacetonato)platinum catalyst in toluene. Network structures of the resulting gels, mesh size, and mesh size distribution were quantitatively characterized by means of a novel scanning microscopic light scattering (SMILS). The effects of the monomer concentration in the resulting gels were investigated, and gels with homogeneous network structure formed by 1.4 to 1.6 nm size of mesh were obtained under the monomer concentrations that are relatively higher than the critical gelation concentration. The mesh sizes of gels, that were determined with SMILS, with DD were larger than those with HD and were independent of the nature of the cross-linking reagents. The TMCTS-HD gel formation process was successfully traced with SMILS. The result indicates the formation of microgels in the early stages of the reaction following aggregation of the microgels, extension of the microgels, or both to form the infinite network that occupies the space of the reaction system around the gelation point. Photo-pattern coating of a glass plate with the POSS-DD gel was achieved by means of the photo hydrosilylation reaction of the cast reaction medium.

Shrinking Behavior of Surfactant‐Grafted Thermosensitive Gels and the Mechanism of Rapid Shrinking

AbstractSurfactant‐grafted hydrogels with a fast response to temperature were prepared. In order to clarify the mechanism of rapid shrinking, the effects of the grafted surfactant and the homogeneity of the main chain were investigated. Poly(NIPAAm‐co‐S180A) gels prepared using a chemical cross‐linker (bis‐PNS gels) exhibited rapid shrinking, as did PNS gels prepared by γ‐ray irradiation (γ‐PNS gels). This suggested that the rapid shrinking of the PNS gel did not depend on the homogeneity of the main‐chain structure. The shrinking kinetics of the bis‐PNS gels depended on the amount of the introduced surfactant, which means that shrinking is enhanced by micelle formation as a dynamic driving force. From the analysis by dynamic light scattering (DLS) and scanning microscopic light scattering (SMILS), it was suggested that the micelle structure, which induced rapid shrinking, existed in the bis‐PNS gel.magnified image

End-Crosslinking Gelation of Poly(amide acid) Gels studied with Scanning Microscopic Light Scattering

Network formation in the gelation process of end-crosslinked poly(amide acid) gels, which are the precursor of end-crosslinked polyimide gels, was studied by scanning dynamic light scattering. The gelation process is essentially non-reversible due to the formation of covalent bonds. The molecular structure formed in the gelation process is controlled by varying the equivalence ratio of end-crosslinker to oligomer during the preparation. It was found that a couple of relaxation modes are observed in the gelation point even for semi-rigid poly(amide acid) solutions. This is similar to flexible polymer solutions and convenient to characterize the molecular structure in the gelation processes. The fast mode is related to the cooperative diffusion process of the network structure formed by over lapped macromolecules, i.e., gel mode, which determines the averaged mesh-size of the network structure. The slow mode is related to the relaxation time of the formation of the transient network structure, which shows a slowing down close to the gelation point and disappears after gelation due to the formation of the permanent network structure.