Introduction: The design of smaller, faster, more efficient devices is a major scientific and technological challenge, driven in part by a constant need for smaller features and higher resolution patterns. To this end, self-assembling soft materials[1],[2] continue to play an important role in societal and economical goals for smaller and hierarchically nanostructured devices. Block copolymer thin films belong to this class of materials where self-assembly takes place on nanometer length scales. This makes them ideal for emerging nanotechnologies, including applications, for instance, in nano-templating, nano-porous membranes, organic optoelectronics and anti-reflection coatings. Nano-organized thin films are made today from synthetic di-block copolymers (petroleum) and their self-assembly is constrained to 20 nm resolution (domain and size spacing). This is a consequence of the small incompatibility between both blocks (typical model system: PS-PMMA)[3]. To make those systems more attractive for bit-patterned media applications, attempts were made to achieve smaller domains and sizes. These attempts have, however, had only limited success.
Materials and Methods: Indeed, to date, numerous studies have been focused on the self-assembly of petroleum-based BCPs for potential applications in multidisciplinary fields, such as nanoparticles for drug delivery, or nano-organized films for biosensors, or nanolithography, etc. Such materials are derived from fossil resources that are being rapidly depleted and have negative environmental impacts. In contrast, carbohydrates are abundant, renewable and constitute a sustainable source of materials. Such materials (bio-sourced block copolymer systems) have been obtained using "click" chemistry consisting of linking oligo/polysaccharide to another block (synthetic or natural). Those bio-based systems are currently attracting much interest in various sectors and their industrial applications at the nanoscale level will have to expand quickly in response to the transition to a bio-based economy.
Results and Discussion: To overcome these two bottlenecks -substitution of petroleum molecules and resolution limit - R. Borsali et al[3]-[6] have recently made an important breakthrough by using carbohydrate-based block copolymer and have achieved the highest resolution ever reached to date (5 nm features)-(see illustrations on Figures 1 and 2).
We will in this paper present new and recent results on the self-assemblies of oligosaccharide-based block copolymer (synthetic block-Maltoheptaose, where synthetic block stands for Polystyrene or Polyisoprene) leading to highly nanostructured thin films (sub-10nm resolution).
Conclusion: This new class of carbohydrate based-block copolymer systems lead to nano-organized thin films (resolution sub_10nm) that could open the horizon to numerous applications in flexible opto-electronics, biosensors, photovoltaic cells and new generation of nanolithography.
The authors acknowledge the CNRS, Greenanofilms project (Seventh Framework Program under grant agreement n° 603519), Institut Carnot Polynat and Labex ARCANE for financial supports.
References:
[1] Giacomelli, C., Schmidt, V., Aissou, K. And Borsali, Langmuir 26 (20), 15734-15744 (2010)
[2] K. Aissou,; R. Borsali, S. Fort, S. Halila,,T. Baron, “Nano-Organized Thin Films Obtained From Glycopolymer Maltoheptose-Ps System. Inventors: “ Patent (Cnrs) 2010, World Extension 2011
[3] K. Aissou, I. Otsuka, C. Rochas, S. Fort, S. Halila, & R. Borsali Langmuir, 27(7), 4098-4103 (2011)
[4] Cushen, J.; Otsuka I; Bates, C.; Halila, S.; Fort, S.; Rochas, C.; Easley, J.; Rausch, E.;Thio, A.; Borsali, R.; Willson, G.; Ellison, C. Acs Nano, 6(4), 2012, 3424-3433
[5] Y.C. Chiu, I. Otsuka, S. Halila, R. Borsali & W.C. Chen, High-Performance Nonvolatile Transistor Memories Of Pentacence Using The Green Electrets Of Sugar-Based Block Copolymers And Their Supramolecules, Adv. Funct. Mater., 24(27), 2014, 4240-4249
[6] Yu-Cheng Chiu, Han-Sheng Sun,
Wen-Ya Lee,
Sami Halila, Redouane Borsali,
Wen-Chang Chen
”Oligosaccharide Carbohydrate Dielectrics toward High-Performance Non-volatile Transistor Memory Devices. Article first published online: 1 SEP 2015 | DOI: 10.1002/adma.201502088 – Advanced Materials