title: DNA ionogel: Structure and self-assembly.
abstract: DNA dissolved in ionic liquid (IL) solution (1-ethyl-3-methylimidazolium chloride, [C2mim][Cl]) showed a transition to the gel phase ([DNA] ≥ 1% (w/v)). The gelation time was 400 s for the 1% [IL] sample which reduced to 260 s for 5% [IL] concentration. Gelation times, obtained from the viscosity and ergodicity breaking from the dynamic structure factor data, were remarkably identical to each other. Correspondingly, the gelation temperature which was ∼60 °C increased to 67 °C with [IL] content. The small angle neutron scattering (SANS) structure factor profile revealed the presence of the following three distinct length scales: (a) mesh size, ξ ≈ 3 ± 0.5 nm for ionogels, and ≈0.73 ± 0.06 nm, for sol; (b) cross-sectional radius of DNA strand, Rc≈ 1.6 ± 0.1 nm; and (c) the characteristic inter-cluster distance ≈33 ± 5 nm. Physical conformation of the DNA-IL complexes remained close to the Gaussian coil definition. It was observed that without IL, in the sol phase, the system was completely ergodic and did not gel, while on addition of IL a sudden transition to the non-ergodic (arrested) gel phase occurred. This was due to the formation of an amorphous network of DNA-IL complexes preceding gelation. In summary, it is shown that the DNA ionogels can be prepared with a tunable gel strength (27-70 Pa) and gelation temperature (60-67 °C). Further, the relaxation dynamics was found to be hierarchical in IL content of the gel, revealing considerable self-organization.
authors.affiliation: School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India.
authors.forename: Pankaj Kumar
authors.initials: PK
authors.lastname: Pandey
authors.affiliation: Special Center for Nanosciences, Jawaharlal Nehru University, New Delhi 110067, India. bohi0700@mail.jnu.ac.in kamla.jnu@gmail.com and Inter University Accelerator Centre, New Delhi 110067, India.
authors.forename: Kamla
authors.identifier: http://orcid.org/0000-0003-3825-376X
authors.initials: K
authors.lastname: Rawat
authors.affiliation: State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
authors.forename: V K
authors.initials: VK
authors.lastname: Aswal
authors.affiliation: Laboratory for Neutron Scattering, Paul Scherrer Institut, Villigen, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Kohlbrecher
authors.affiliation: School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India and Special Center for Nanosciences, Jawaharlal Nehru University, New Delhi 110067, India. bohi0700@mail.jnu.ac.in kamla.jnu@gmail.com.
authors.forename: H B
authors.initials: HB
authors.lastname: Bohidar