Biomimetic, hierarchical structures on polymer surfaces by sequential imprinting (original) (raw)
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Hierarchical polymeric architectures through molecular imprinting in liquid crystalline environments
European Polymer Journal, 2018
The use of liquid crystalline (LC) media as sacrificial templates during the polymer synthesis has been explored. The LC-media introduce morphological features into resultant polymers which when used together with molecular imprinting can produce materials with hierarchical architectures. Bupivacaine (1) imprinted co-polymers of 2-hydroxyethylmethacrylate (HEMA) (2a) and 1,4-divinylbenzene (DVB) (3a) were synthesized using photochemical initiation in lyotrophic liquid crystalline phases of AOT (5) in water/p-xylene and Triton X-100 (6) /water systems. SEM studies revealed the impact of the LC-media on polymer morphology, with polymer brushlike structures, with bristles of ≈30 nm diameter. The polymer morphology reflects that of the hexagonal phase of the LC medium. The rebinding characteristics of polymer films were evaluated quartz crystal microbalance (QCM, under FIA conditions). The influence of the presence of imprinting-derived recognition sites in AOT (5) in water/p-xylene polymer film induced brush-like features which provided a 25-fold enhancement of sensor sensitivity. This chemosensor was shown to be selective for the local anesthetic template, bupivacaine, through studies using the structural analogues ropivacaine and mepivacaine.
ACS Omega, 2018
The surface relief structure of polymer films over large areas can be controlled by combining nanoscale imprinting and microscale ultraviolet−ozone (UVO) radiation, resulting in hierarchical structured surfaces. First, nanoscale patterns were formed by nanoimprinting elastomer [poly(dimethylsiloxane) (PDMS)] films with a pattern on a digital video disk. Micron-scale patterns were then superimposed on the nanoimprinted PDMS films by exposing them to ultraviolet radiation in oxygen (UVO) through a transmission electron microscopy grid mask having variable microscale patterning. UVO exposure leads to conversion and densification of PDMS to SiO x , leading to micron height relief features that follow a linear scaling relation with pattern dimension. Further, the pattern scopes are shown to collapse into a master curve by normalized feature values. Interestingly, these relief structures preserve the nanoscale features. In this paper, the influence of the self-limiting PDMS densification, wall stress at the boundary of micro-depression, and UVO exposure energy is studied in control of the micro-depression scale. This simple two-step imprinting process involving both nanoimprinting and UV radiation allows for facile fabrication of the dimension adjustable micro−nano hierarchically structures not only on elastomer films but also on thermoplastic polymer films. Coarse-grained molecular dynamics simulations were performed to correlate the surface tension and elastic properties of polymeric materials to the deformation of the pattern structure.
A morphological study of molecularly imprinted polymers using the scanning electron microscope
Analytica Chimica Acta, 2006
Molecular imprinting is an emerging technique for producing polymers with applications in affinity-based separation, in biomimetic sensors, in catalysis, etc. This variety of uses relies upon the production of polymers with different affinities, specificities, sensitivities and loading capacities. Research into the development of molecular imprinted polymers (MIPs) with new or improved morphologies -which involves modification of the polymerisation process -is therefore underway. This paper reports a comparative study of non-covalent MIPs synthesised by "bulk" polymerisation using digoxin as template. These were synthesised under different conditions, i.e., changing the functional monomers employed (methacrylic acid or 2-vinylpyridine), the porogens (acetonitrile or dichloromethane) used, and by altering the volume of the latter. The polymerisation process was allowed to proceed either under UV light or in a thermostat-controlled waterbath. The surface morphology (was determined by scanning electron microscopy) and the ability of the different polymers to selectively rebind the template was then evaluated.
Polymer Imprint Lithography with Molecular-Scale Resolution
Nano Letters, 2004
We show that small diameter, single-walled carbon nanotubes can serve as templates for performing polymer imprint lithography with feature sizes as small as 2 nm − comparable to the size of an individual molecule. The angstrom level uniformity in the critical dimensions of the features provided by this unusual type of template provides a unique ability to investigate systematically the resolution of imprint lithography at this molecular scale. Collective results of experiments with several polymer formulations for the molds and the molded materials suggest that the density of cross-links is an important molecular parameter that influences the ultimate resolution in this process. Optimized materials enable reliable, repetitive patterning in this single nanometer range.
A comparison of thermally and photochemically cross-linked polymers for nanoimprinting
Microelectronic Engineering, 2003
The characteristics and benefits of two types of cross-linking prepolymers with low glass transition temperature (T ) for nanoimprinting are reported. They are soluble in organic solvents and their solutions can be g processed like those of common thermoplastics. The imprinted patterns receive high thermal and mechanical stability through cross-linking polymerization. The course of the polymerization was investigated to determine the appropriate conditions for the imprint process. In thermally cross-linked polymers mr-I 9000, the cross-linking occurs during imprinting. Process time and temperature depend on the polymerization rate. Volume shrinkage during the polymerization does not adversely affect imprinting. Photochemically cross-linked polymers mr-L 6000 make possible imprint temperatures below 100 8C and short imprint times. The T of the g prepolymer determines the imprint temperature. The cross-linking reaction and structural stabilization is performed after imprinting. 50-nm trenches and sub-50-nm dots confirm the successful application of the polymers.
Molecular Imprinting Technology for Biomimetic Assemblies
Hacettepe Journal of Biology and Chemistry, 2020
The term biomimetic can be simply defined as the examination of nature. The scientists inspired by the enormous diversity of nature to solve human problems or facilitate daily life by mimicking natural models, systems, and elements especially in the biomedical and therapeutic applications to make better drugs, artificial organs, sensing instruments, etc. Biological recognition elements like proteins, antibodies, enzymes, DNA, lectins, aptamers, cells, and viruses have been heavily used to ensure specificity in such applications in spite of their lack of stability and reusability. However, in the last two decades molecularly imprinted polymers, MIPs, have been synthesized as an alternative to mimic natural biological interactions for a broad spectrum of templates by means of coordinating functional monomers around template in the presence of cross-linker. This review will outline the broad contours of biomimetics prepared by molecular imprinting techniques and their practical applica...
Solvo-selective imprinting of a thin polymer blend film for creating multi-length scale patterns
Bulletin of Materials Science, 2020
Controlling and spatial ordering of the phase separation in ultra-thin polymer-blend films is a viable approach to create complex surface structures with unique properties. This study reports a facile solvo-selective patterning technique in a phase-separated polymer blend thin film comprising of immiscible polymers polystyrene (PS) and poly(methyl methacrylate) (PMMA). The pattern replication was achieved using capillary force lithography by imprinting the blend films with cross-linked polydimethylsiloxane stamp with grating patterns. The replication was done in the presence of 1-chloropentane or acetic acid vapours, which are selective solvents for PS and PMMA, respectively. This engendered capillary flow of only one phase while the domains of the second phase remain rigid. Depending on the initial as-cast morphology of the film which is a function of the relative proportion of PS and PMMA, a variety of structures were obtained by combining the phase-separated domains with the structure imposed by the stamp. This method can be considered as a simple, one-step technique for creating hierarchical patterns that are likely to find applications in modulating properties of soft surfaces.
Journal of Nanoscience and Nanotechnology, 2009
A highly durable imprint template is essential for the industrialization of nanoimprint lithography (NIL). Conventionally, Si-based materials were used for the fabrication of imprint templates. However, their fabrication is very expensive and they can be easily damaged during repeated imprint processes due to their brittleness and poor mechanical properties. The Ni template has excellent mechanical strength and can be easily and cheaply duplicated by the electroforming process. It has the potential for application to the NIL process if its poor antistiction property, which causes serious detaching issues, is improved. In this study, thin Au and Ti layers were deposited on a Ni template and a thiol-based, hydrophobic, self-assembled monolayer (SAM) layer was stably formed on the Au coated Ni template. Thus, the antistiction property of the Ni template was drastically elevated. Using the prepolymer-based, thermal imprint process and the thiol-based, SAM-coated Ni template, sub-micron sized patterns were successfully formed on the Si substrate.