Preface

Innovation of bio-resources and advanced material based on colloid interface and soft-matter

Yasuhisa Adachi*, Katsuhiko Ariga**

*University of Tsukuba, **National Institute for Material Science

One of the remarkable characteristics of Tsukuba area in the field of colloid and interface and soft-matter is that a great number of foreign researchers and foreign pH-D students are working in different institutes such as NIMS, AIST and Tsukuba University. Colloid and interfaces, are commonly related to material science and bio-resources, such as food, soil, microbiology and human health care. It can be easily imagined that the interactions between different source of institute and field with an common interest of colloid and interface has a big potential for future innovation. However, so far, the chance for such meeting is rare. In order to improve this situation, we organize a session of colloidal dispersion and soft-matter from various institutes to discuss the potentiality for future innovation.

Soft matter, Colloid, Interface, Bio-resources, material

Dynamics of colloidal flocculation with polyelectrolyte

Lili Feng1 and Yasuhisa Adachi2

1School of Water Resources, North China University of Water Resources and Electric Power. 2School of Life and Environmental Sciences, University of Tsukuba.

Flocculation dynamics of polystyrene latex particle with polycations, similar in the molecular weight (Mw= 5×106 g/mol) but different in the charge density (σ=1 and 0.04), is analyzed at various ionic strengths (L. Feng, M.C. Stuart, Y.Adachi, Adv. Colloid Int. Sci., 226: 101-114, 2015). The high charge density polycation induces the flocculation of colloidal particles mainly though patch-wise interaction/electrostatic interaction, while the flocculation of colloidal particles with the low charge density polycation is mainly controlled by bridging and steric effect.

The flocculation of colloidal particles subjected to Brownian motion or in the mixing flow is accelerated by the addition of the high charge density polycation at the isoelectric point (L. Feng, Y.Adachi, A. Kobayashi, Colloid Surfaces A, 440:155-160,2014). The acceleration of flocculation originates from the additional electrostatic attraction between bare parts of one particle and polyelectrolytes covered parts of neighboring particles (L.Feng, Y. Adachi, M. Kobayashi, Colloid Surfaces A, 471:38-44,2015). Due to the screening electrostatic interaction at high ionic strength, the acceleration of rate is more predominant for salt-free, decreases with increasing ionic strength, and vanishes above a certain ionic strength.

The rate of perikinetic flocculation of colloidal particles is reduced with addition of the low charge density polycation, even at the optimum dosage (L.Feng, Y. Adachi, Colloid Surfaces A, 454:128-134,2014). The reduction of perikinetic flocculation is due to the competing effect of bridging with steric effect. However, the low charge density polycation could accelerate the orthokinetic flocculation though “bridging” in the initial two dozens minutes, but with continuous adsorption of polyelectrolytes and relaxation of pre-adsorbed chains steric effects sets in, and thus slows down the flocculation process (L.Feng, M. Kobayashi, Y. Adachi, Colloid Polymer Sci., 293(12):3585-3593, 2015).

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Assembly of polyelectrolytes: towards soft nanoparticles for functional materials

Junyou Wang1, 2 Aldrik Velders,2 Jasper van der Gucht3 and Martien CohenStuart1,3

1State-Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237,

People’s Republic of China

2Laboratory of BioNanoTechnology, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands 3Laboratory of Physical Chemistry and Soft Matter, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The

Netherlands

Polyelectrolytes are polymers with a substantial portion of the constitutional units containing ionic or

ionisable groups. Assembly of polyelectrolytes demonstrates a facile and straightforward strategy to organize the

macromolecules into highly ordered nano- or micro-structures. Here, we focus on the self-assembly of functional

polyelectrolytes including: metal-ligand coordination polymer, dendrimer, block copolymer, polypeptide and

conjugated polymer, leading to hybrid micelles and hydrogels as functional soft materials. (Junyou Wang et al.

Chem. Eur. J. 2017, 23, 239; Soft Matter 2016,12, 99, Chem. Commun. 2013,49, 3736; Macromolecules 2012,

45, 8903; Macromolecules 2012, 45, 7179) For example, we perform a serial studies on the iron and lanthanide

(Gd3+, Eu3+) containing hybrid micelles, investigating the formation, stability and corresponded magnetic and

fluoresce properties in detail. The study goal is developing this class of micelle as NMR contrast agent and

fluorescence imaging probes. Assembly of diblock polyelectrolyte and conjugated polymer develops a new

mechanical sensor; and mixing the polypeptide and coordination structures build up the virus-like nano-rods.

Investigating these assembly systems is very interesting from not only the fundamental point of view, but also

the applied standpoints due to the introduced properties and functions, showing great potential for developing

soft structures and functional materials.

Functional soft structures and materials obtained by assembly of different polyelectrolytes

M.A. Cohen Stuart

Softness as a key to successful ‘Pickering’ stabilization

Abstract

Emulsions and foams often suffer loss of stability due to disproportionation, that is, the Laplace pressure drives transport from small to large bubbles or droplets. Solubility, diffusivity and temperature are among the parameters that determine the rate of disproportionation, but for a given two-phase system one cannot change these. The only remaining parameter allowing control is the interfacial tension. Common surfactants can lower interfacial tension to a finite value, but this is often insufficient to stop disproportionation, in particular droplet shrinking; particulate (Pickering) stabilizers adhere very strongly to fluid interfaces and can often stop disproportionation by reducing the interfacial tension to very low values. Yet, they are often not successful foamers or emulsifiers, because they have to overcome a repulsive barrier when attaching to the interface, which leads to a very slow adsorption rate. We discuss a robust and successful alternative, namely core-shell particles with a hard core and a soft, solvent-swollen shell. This shell allows easy attachment by bridging of polymer chains, and therefore such particles adsorb at diffusion-controlled rates. Emulsions formed in this way are very stable, and even feature non-spherical droplets, signaling ultralow interfacial tension. Foams with enhanced stability are also readily formed.

Polycation macromolecule architecture as a key to manipulation for polymer/liposome complexes properties

Andrey Sybachin and Alexander Yaroslavov

Polymer Department, Faculty of Chemistry, Lomonosov Moscow State University

Spherical lipid bilayer vesicles - liposomes are widely used as nanocontainers for the delivery of bioactive substances. Hydrophilic molecules could be incorporated in inner water cavity of the liposomes while hydrophobic agents could be included in fatty tails area. Modification of liposomal membrane with polyelectrolytes allows one to significantly improve properties of nanocontainer- increase of mechanical and thermodynamical stability, imparting of vector properties, manipulate with release properties etc. In present work we discuss how the evolution of polyelectrolyte architecture affect the structure and properties of the resulted polymer/liposomes complexes. In this investigation we have studied features of formation of the complexes between anionic liposomes and polycations. The used range of the polycations involved quaternized polyvinylpyridines with different molecular weight, star-shaped polycations with different number of arms, polycationic brushes and microgels. The properties of the interfacial complexes were studied with focusing on reversibility of the polymer to vesicle interaction in water-salt media, geometry of the adsorbed macromolecule, lateral segregation and trans-membrane migration of the lipids induced by polyelectrolyte and cytotoxicity of the complexes (Yaroslavov A et al., Adv Colloid Interface Sci 226: 54-64, 2015). The role of the macromolecule chain length and architecture was demonstrated to be of great importance on manipulating “host – guest” roles between liposome and polymer. The collected data allows one to predict properties of polyelectrolyte/vesicle complexes and to create liposomal nanocontainers with desired features.

This work was supported in part by Russian Foundation for basic Research (project #17-03-00433)

Dynamic Light Scattering Studies of Interpolymer Complex Formation between

Poly(N-Isopropylacrylamide) and Poly(Acrylic Acid)

Kazuyoshi Ogawa1, Atsushi Tsuyukubo2

1Faculty of Life and Environmental Sciences, University of Tsukuba 2Graduate School of Life and Environmental Sciences, University of Tsukuba

Intermolecular polymer complexes (IPCs) are formed by specific cooperative interactions between two or more complementary polymers in (aqueous) solution. The type of IPCs depend on the nature of the associating polymers or materials and the interactions causing (inducing) complex formation. The interactions are mainly classified into electrostatic interaction, hydrogen-bonding, hydrophobic interaction, van der Waals forces. The type and strength of interactions depends on not only solution parameters such as pH, ionic strength, and temperature but also the solution properties polymer (molecular weight). Interpolymer complex (IPC) formation studies using simple synthetic polymers would help understanding the mechanism of assembly-phenomena of molecules observed in biological system achieved by intermolecular interactions which act at same time in a complicated manner, concertedly and never separatedly. In our study, conformation change of poly(N-isopropylacrylamide) (PNIPA) by hydrogen bonding IPC formation with poly(acrylic acid) (PAAc) in aqueous solution was studied by laser light scattering and isothermal titration at different pH. The complex was prepared by titrating the solution of PAAc with short polymer chain to that of PNIPA with long polymer chain at 25 °C in 1 mM NaCl. The resulting complexes are divided into three types: (i) water-soluble intrapolymer complexes consisting of a PNIPA to which PAAc chains bind (ii) complex coacervates composed of aggregated intrapolymer complexes, and (iii) insoluble amorphous precipitates. These types depend on not only pH and but also the mixing ratio of PAAc to PNIPA. In the formation of water-soluble intrapolymer complexes, the shrinking of PNIPA complexed with PAAc was observed. In isothermal titration calorimetry, the shrinking or aggregation of PNIPA by complex formation with PAAc was endotherm. That suggested that not only hydrogen bond but also hydrophobic interaction works concertedly in IPC formation between PNIPA and PAAc.

Effect of interlamellar interactions on shear induced multilamellar vesicle formation

Youhei Kawabata1, Robert Bradbury2,3, Shiori Kugizaki1, Kathleen Weigandt3, Yuri. B. Melnichenko4, Koichiro

Sadakane5, Norifumi L. Yamada6, Hitoshi Endo6, Michihiro Nagao2,3, and Hideki Seto6

1Department of Chemistry, Tokyo Metropolitan University.

2Center for exploration of Energy and Matter, Department of Physics, Indiana University. 3NIST Center for Neutron Research, National Institute of Standards and Technology.

4Biology and Soft Matter Division, Oak Ridge National Laboratory. 5Faculty of Life and Medical Sciences, Doshisha University.

6Institute of Materials Structure Science, High Energy Accelerator Research Organization.

Shear-induced multilamellar vesicle (MLV) formation has been studied by coupling the small-angle neutron

scattering (SANS) technique with neutron spin echo (NSE) spectroscopy. A 10% mass fraction of the nonionic

surfactant pentaethylene glycol dodecyl ether (C12E5) in water was selected as a model system for studying weak

inter-lamellar interactions. These interactions are controlled either by adding an anionic surfactant, sodium dodecyl

sulfate (SDS), or an antagonistic salt, rubidium tetraphenylborate (RbBPh4). Increasing the charge density in the

bilayer induces an enhanced ordering of the lamellar structure. The charge density dependence of the membrane

bending modulus was determined by NSE, and showed an increasing trend with charge. This behavior is well

explained by a classical theoretical model.

By considering the Caillé parameters calculated from the SANS data, the layer compressibility modulus B is

estimated and the nature of the dominant inter-lamellar interaction is determined. Shear flow induces MLV

formation around a shear rate of 10 s-1, when a small amount of charge is included in the membrane. The flow-

induced layer undulations are in-phase between neighboring layers when the inter-lamellar interaction is

sufficiently strong.

Under these conditions, MLV formation can occur without significantly changing the inter-lamellar spacing.

On the other hand, in the case of weak inter-lamellar interactions, the flow-induced undulations are not in-phase,

and greater steric repulsion leads to an increase in the inter-lamellar spacing with shear rate. In this case, MLV

formation occurs as the amplitude of the undulations gets larger and the steric interaction leads to in-phase

undulations between neighboring membranes (Kawabata Y et al., J. Chem. Phys. 147: 035905, 2017).

Figure 1 (a)(b) 2D SANS patterns from RbBPh4/C12E5/D2O system at C = 0.001 for different

shear rate of (a) radial and (b) tangential configurations.

Experiments and modeling on the charging and aggregation of cellulose nanofibers in aqueous solutions

Yusuke Sato1, Yasuyuki Kusaka 2 and Motoyoshi Kobayashi3

1Graduate School of Life and Environmental Sciences, University of Tsukuba.2National Institute of Advanced Industrial Science and Technology.

3Faculty of Life and Environmental Sciences, University of Tsukuba.

To better understand the charging and aggregation of cellulose nanofiber (CNF), we measured the number of de-protonated groups of CNF by potentiometric titration, the electrophoretic mobility, and the hydrodynamic size by dynamic light scattering as a function of pH and KCl concentration. We found that the pH-dependent charging is described by the 1-pK Poisson-Boltzmann model and the Ohshima equation considering the relaxation of electric double layer for a cylinder. Also, we calculated the capture efficiency of aggregation for perpendicularly and parallelly interacting cylinders using Derjaguin, Landau, Verwey, and Overbeek theory. From the comparison of the capture efficiency with the measured hydrodynamic diameter, we suggest that CNFs can be aggregated in perpendicular orientation at low pH and low salt concentration, and the fast aggregation regime of CNF is realized by the reduction of electric repulsion for both perpendicularly and parallelly interacting CNFs. Meanwhile, the application of Smoluchowski’s equation to the electrophoretic mobility underestimates the zeta potential and the repulsive interaction.

email: kobayashi.moto.fp@u.tsukuba.ac.jp

Development of self-oscillating polymer

gel actuators and robots

Yusuke Hara

National Institute of Advanced Science and Technology (AIST),

Central 5-2, 1-1-1 Higashi, Tsukuba 305-8565, Japan,

E-mail:y-hara@aist.go.jp

Recently, many kinds of soft actuators have been much studied. In particular,

stimuli-sensitive gels that swell or shrink by the external stimuli have been

applied to the many type of soft actuators. In order to drive these gel actuators,

the external control devices and battery must be needed. On the other hands, in

biological systems, without on-off switching of the external stimuli, the motion

generates by directly changing from the chemical energy to mechanical energy

in the body. In this study, in order to construct the biomimetic soft actuator

that do not need the external controller and battery like a living organism, we

utilized the self-oscillating polymer gel actuators. The energy source of the

self-oscillating polymer gel actuators are the oscillatory Belousov-Zhabotinsky

(BZ) reaction (See Fig.1). The BZ reaction is well known as a nonequilibrium

dissipative system, and generates self-oscillations under the constant

temperature conditions. The overall process of the BZ reaction is the oxidation

of an organic substrate by an oxidizing agent in the presence of the catalyst

under acidic conditions.

Fig. 1 The oscillatory Belousov-Zhabotinsky (BZ) reaction under the

constant temperature condition.

In the BZ reaction process, the oxidation states of the metal catalyst moiety

change periodically: Ru(bpy)32+ ↔ Ru(bpy)3

3+. In the oxidized state

(Ru(bpy)33+), the Ru metal catalyst has the hydrophilic property, and the

reduced Ru catalyst (Ru(bpy)32+) has the hydrophobic property. When the Ru

catalyst is covalently bonded to the NIPPAm polymer main-chain into the self-

oscillating polymer gel, the polymer gel undergoes the oscillating volume

changes (swelling-deswelling self-oscillation) because the solubility of the Ru

catalyst moiety changes synchronized with the BZ reaction. In this

presentation, I will introduce the detail mechanism of the self-oscillating

behavior of the autonomous polymer gel actuators. Moreover, I will introduce

the many types of the self-oscillating polymer gel actuators and soft robots

made by the autonomous gel actuators.

【References】

1. Zaikin, A.N.; Zhabotinsky, A.M. Concentration wave propagation in two-

dimensional liquid-phase self-oscillating system. Nature 1970, 225, 535–537.

2. Reusser, E.J.; Field, R.J. The transition from phase waves to trigger waves in

a model of the Zhabotinskii reaction. J. Am. Chem. Soc. 1979, 101, 1063–

1071.

3. Scott, S.K. Chemical Chaos, 1st ed.; Oxford University Press: Oxford, UK,

1991.

4. Field, R.J.; Burger, M. Oscillations and Traveling Waves in Chemical

Systems; John Wiley & Sons: New York, NY, USA, 1985.

5. Ishiwatari, T.; Kawaguchi, M.; Mitsuishi, M. Oscillatry reactions in polymer

systems. J. Polym. Sci. Polym. Chem. 1984, 22, 2699–2704.

6. Yoshida, R.; Takahashi, T.; Yamaguchi, T.; Ichijo, H. Self-oscillating gel. J.

Am. Chem. Soc. 1996, 118, 5134–5135.

7. Yoshida, R.; Sakai, T.; Ito, S.; Yamaguchi, T. Self-oscillation of polymer

chains with rhythmical soluble-insoluble changes. J. Am. Chem. Sci. 2002,

124, 8095–8098.

8. Hara, Y.; Yoshida, R. Self-oscillation of polymer chains induced by the

Belousov-Zhabotinsky reaction under acid-free conditions. J. Phys. Chem. B

2005, 109, 9451–9454.

9. Hara, Y.; Yoshida, R. A viscosity self-oscillation of polymer solution induced

by the BZ reaction under acid-free condition. J. Chem. Phys. 2008, 128,

224904.

10. Hara, Y.; Yoshida, R. Control of oscillating behavior for the self-oscillating

polymer with pH-control site. Langmuir 2005, 21, 9773–9776.

11. Y. Hara, H. Mayama, Y. Yamaguchi, Switching the BZ Reaction with a

Strong-Acid-Free Gel, The Journal of Physical Chemistry B, 2014, 118, 634–

638.

12. Y. Hara*, H. Mayama, K. Morishima, Generative Force of Self-oscillating

Gel, The Journal of Physical Chemistry B, 2014, 118, 2576-2581.

13. Y. Hara*, Development of autonomous actuators and application to micro

fluid devices, Drug Delivery System, 2013, 28, 127-134.

Correlation between hydration states and aggregation structures of lipids studied by THz spectroscopy

Mafumi Hishida

Department of Chemistry, University of Tsukuba.

It has not been fully clarified whether water has a crucial role for the self-assembly of soft materials or it is just a homogeneous background. Recently we have investigated hydration states of phospholipids, the main constituent of biomembranes, using THz spectroscopy. By this method, water dynamics is precisely observed in ps time scale, indicating slight change in the water dynamics can be precisely detected and the slightly bound water at the surface is evaluated. In the lamellar phase of the lipids, the water layer thickness between the lipid bilayers is about 2.5 nm, that corresponds to about 10 layers of water molecules. It was reported that only one layer of strongly bound water exists at the surface. On the other hand, we found that most of the inter-lamellar water is regarded as a hydration water including the slightly bound water, whose rotational relaxation dynamics is slower than bulk water [1]. The spectrum of the inter-lamellar water extracted by the Bruggeman’s theory indicates that hydrogen-bonds are disturbed or destroyed in the water layer [2]. The long-range hydration state depends strongly on the chemical structure of the lipid head groups, implying the different phase transition behavior of these lipids is dominated by the hydration states [3]. The hydration state of a nonionic surfactant was also measured and it was found that the hydration state changes accompanied by the structural phase transition [4]. The change in the hydration state during the phase transition is also observed for phospholipid systems [2]. These results indicate that the water has a stronger effect on the self-assembly of lipids and surfactants than we have believed so far.

[1] M. Hishida, K. Tanaka, Phys. Rev. Lett., 106, 158102, (2011). [2] Y. Hemmi, M. Hishida, Y. Yamamura, K. Saito, in preparation. [3] M. Hishida, K. Tanaka, Y. Yamamura, K. Saito, J. Phys. Soc. Jpn., 83, 044801 (2014). [4] M. Hishida, K. Tanaka, J. Phys.: Condens. Matter 24, 284113 (2012).

Self-Assembled Fullerene Crystals at Liquid-Liquid Interface: From Zero to Higher Dimensions

Lok Kumar Shrestha*, Rekha Goswami Shrestha, Partha Bairi, Jonathan P. Hill, Katsuhiko Ariga

International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Ibaraki Tsukuba 305-0044, Japan

We present a simple recipe of producing self-assembled fullerene C60 and C70 nano/microcrystals from zero to higher dimensions using solution based strategy called liquid-liquid interfacial precipitation (LLIP) method under mild conditions of temperature and pressure [1]. We also discuss the recently developed novel technique for the expansion of fullerene nanomaterials into hierarchic macro- and mesopores architectures with crystallized frameworks [2]. These novel materials offered enhanced surface textural properties compared to pristine fullerenes and it could be flexibly controlled by adjusting the synthetic conditions. We also discuss our recent results on the thermal conversion of single crystalline fullerene crystals (tubes to cubes) into high surface area nanoporous graphitic carbons [3,4]. The fullerene crystals derived graphitic carbon materials displayed enhanced electrochemical supercapacitive performance followed by excellent sensing performance sensitive towards aromatic solvents. Note that the C60 molecule can be regarded as an ideal zero dimensional building blocks with striking functions. Therefore, construction of zero to higher-dimensional objects, such as 1D, 2D or 3D including porous nanomaterials may realize important aspects of fullerene nanoarchitectonics [6,7].

References

[1] L. K. Shrestha, Q. Ji, T. Mori, K. Miyazawa, Y. Yamauchi, J. P. Hill and K. Ariga, Chem. –Asian J. 8 (2013) 1662 [2] L. K. Shrestha, Y. Yamauchi, J. P. Hill, K. Miyazawa and K. Ariga, J. Am. Chem. Soc., 135 (2013) 586 [3] L. K. Shrestha, R. G. Shrestha, Y. Yamauchi, J. P. Hill, et al. Angew. Chem. Int. Ed., 54 (2015) 951 [4] P. Bairi, R. G. Shrestha, J. P. Hill, T. Nishimura, K. Ariga and L. K. Shrestha, J. Mater. Chem. A, 4 (2016) 13899. [5] P. Bairi, K. Minami, W. Nakanishi, J. P. Hill, K. Ariga and L. K. Shrestha, ACS Nano, 10 (2016), 6631 [6] P. Bairi, K. Minami, J. P. Hill, W. Nakanishi, L. K. Shrestha, et al. ACS Nano 10 (2016), 8796. [7] P. Bairi, K. Minami, J. P. Hill, K. Ariga, L. K. Shrestha, ACS Nano 11 (2017), 7790.

Interfacial Phenomena in Printed Electronics

Yasuyuki Kusaka1

1 Flexible Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST).

Printed electronics has emerged as next-generation manufacturing tools of functional devices because printing techniques are expected as fast, cost-effective and environmentally benign processes compared with vacuum-based processing technologies. Many of prototypes including thin film transistors, flexible displays, organic memory devices and various sensors have been demonstrated with formulated functional inks such as metal nanoparticles, organic semiconductors and organometallic precursors made available by state-of-art nanotechnology. In addition to the material design, a deeper understanding on patterning mechanisms and related design/processing rules are prerequisite to establish a reliable and robust printing process. Particularly, mechanisms of reverse offset printing, which is recognized as one of the finest techniques, is highly demanded (Figure 1).

In the reverse offset printing, polydimethylsiloxane (PDMS) exhibiting favorable uptake for particular solvents is used to achieve semi-drying of inks. This feature allows for high-resolution patterning as the solidification of inks is a key factor in keeping structural integrity, and thus resolution of the patterned inks. However, as PDMS is a soft rubber material, its deformation affects the size tolerance of printed patterns. We recently revealed that the horizontal displacement of PDMS upon contacts with cliché reliefs, particularly when two adjacent reliefs are closely located, may worsen the shape integrity of patterns due to the slipping of PDMS. This proximity deformation effect determined by the elasticity, geometrical specifications, and the friction of PDMS is a concept similar to optical proximity corrections (OPC) in photolithography.

On contrary to horizontal displacements, the vertical displacement of PDMS can be favorably used for vertical interconnections. A systematic investigation including PDMS thickness, Young modulus and hole sizes together with a theoretical prediction based on contact mechanics evidenced that a bell-type uplift of PDMS regulates the coverage of contact holes. Related to this, a vapor annealing of ink layers being semi-dried on a PDMS surface effectively generates tapered sidewalls as the absorption of the vapor leads to rewetting of the layers and thus restructuring of their shapes driven by Laplace pressure.

As previously noted, an ink layer shifted to a dried state on a PDMS surface behaves like a solid rather than a liquid. This feature, in turn, allows for the flat cliché version of reverse offset printing. In this method called adhesion contrast planography, a partly VUV-irradiated PDMS, which provides a latent image of stronger adhesion, is used as a cliché. This technique is beneficial in inexpensive cliché fabrications and lower proximity deformation effects because of a uniformly distributed contact pressure.

As seen from the examples shown above, it can conclude that interfacial phenomena including friction, contact deformation, adhesion, absorption and drying play central roles in PDMS-based printing techniques, and therefore we consider that processing rules founded on the interfacial phenomena is a key to realize reliable printed electronics.

Figure 1 (a) Schematic of reverse offset printing. (b) An example of

1/1 μm line-and-space pattern formed with a silver nanoparticle

i k

Self-Aggregation and Interfacial Properties of Sustainable Surfactants Developed from Renewable Feedstock

Avinash Bhadani, Kenichi Sakai, Hideki Sakai, Masahiko Abe

Research Institute for Science & Technology and Department of Pure & Applied Chemistry, Tokyo University of Science,

2641 Yamazaki, Noda, Chiba 278-8510, Japan.

Surfactants consisting of both the hydrophobic and hydrophilic parts find countless application in both consumer and industrial formulations. These molecules are able to adsorb at air-water interface and are able to reduce the surface tension of water. With the demand for the various types of surfactants increasing by each passing year, the current era necessitates development of environmentally benign surfactant molecules containing biocompatible functional moieties. Sustainable surfactants developed from renewable feedstock like fatty alcohols (Bhadani A et al., Langmuir 30: 9036–9044, 2014), fatty acids (Bhadani A et al., RSC Adv 7: 10433–10442, 2017), terpenes (Bhadani A et al., Soft Matter 11: 3076-3082, 2015) etc. can be good alternative to the conventional petrochemical based surfactants. In last decade the sustainable surfactants based on renewable feedstock have witnessed substantial growth due to increase in consumer demand for sustainable products (Foley, P et al., Chem. Soc. Rev 41: 1499–1518, 2012). We in current studies discuss about the synthesis and investigation of new generation of biocompatible ester functionalized cationic and anionic surfactants developed via sustainable approach in our laboratory. These new surfactants are characterized by spectroscopic techniques and further evaluated for their self-aggregation or/and interfacial properties by surface tension, conductivity and scattering techniques. These new surfactants demonstrated superior physicochemical properties compared to the conventional commercially available surfactants. Some of these surfactants were also found to be easily biodegradable. The ease of synthesis combined with superior physicochemical properties makes these surfactants ideal for many application areas and these surfactants can be considered good alternative to conventional petrochemical based surfactants.