Chemoselective Polymer Research Articles

Sensitive Materials and Coating Technologies for Surface Acoustic Wave Sensors

Since their development, surface acoustic wave (SAW) devices have attracted much research attention due to their unique functional characteristics, which make them appropriate for the detection of chemical species. The scientific community has directed its efforts toward the development and integration of new materials as sensing elements in SAW sensor technology with a large area of applications, such as for example the detection of volatile organic compounds, warfare chemicals, or food spoilage, just to name a few. Thin films play an important role and are essential as recognition elements in sensor structures due to their wide range of capabilities. In addition, other requisites are the development and application of new thin film deposition techniques as well as the possibility to tune the size and properties of the materials. This review article surveys the latest progress in engineered complex materials, i.e., polymers or functionalized carbonaceous materials, for applications as recognizing elements in miniaturized SAW sensors. It starts with an overview of chemoselective polymers and the synthesis of functionalized carbon nanotubes and graphene, which is followed by surveys of various coating technologies and routes for SAW sensors. Different coating techniques for SAW sensors are highlighted, which provides new approaches and perspective to meet the challenges of sensitive and selective gas sensing.

Facile preparation of stereochemistry-controllable biobased poly(butylene maleate-co-butylene fumarate) unsaturated copolyesters: a chemoselective polymer platform for versatile functionalization via aza-Michael addition

Biobased stereochemistry-controllable poly(butylene maleate-co-butylene fumarate) unsaturated copolyesters were facilely prepared as a chemoselective polymer platform for versatile functionalization via aza-Michael addition.

Volatile toxic compound detection by surface acoustic wave sensor array coated with chemoselective polymers deposited by laser induced forward transfer: Application to sarin

In this paper we present a sensor array based on surface acoustic wave (SAW) resonators coated with three chemoselective polymers: polyepichlorhydrine (PECH), polyisobutylene (PIB), and polyethylenimine (PEI), deposited by laser-induced forward transfer (LIFT) using a XeCl laser. The targets for the LIFT process were prepared by matrix assisted pulsed laser evaporation (MAPLE). The sensor array was tested upon exposure to dimethyl methylphosphonate (DMMP, a simulant for nerve gases and pesticides containing phosphonate ester groups), dichloromethane (DCM, an industrial applied toxic compound and simulant for choking agents, such as chlorine or phosgene), and ethyl acetate (EtOAc, a wide spread solvent in medical and industrial applications which can be harmful to humans) vapors, and sarin (GB) gas, showing, for each of the sensors, a different sensitivity to the selected chemical agents. The best sensitivities for DMMP and DCM, obtained by using a PECH coated sensor, are 66.23 Hz/ppm and 0.034 Hz/ppm, respectively, whereas the best sensitivity for EtOAc, obtained using PIB, is 0.33 Hz/ppm. A very low concentration (1.8 ppm) of GB was detected within a time to reach the saturation less than 1 min. The measured concentration is below the median lethal dose inhaled (11.3–16.2 ppm min) [1] . A detection limit of 9.24 ppb was calculated for PECH coated sensor exposed to GB.

Matrix-assisted pulsed laser evaporation of chemoselective polymers

In this work, matrix-assisted pulsed laser evaporation was applied to achieve gentle deposition of polymer thin films onto surface acoustic wave resonators. Polyepichlorhydrin, polyisobutylene and polyethylenimine were deposited both onto rigid substrates e.g. Si wafers as well as surface acoustic wave devices using a Nd-YAG laser (266 nm, 355 nm, 10 Hz repetition rate). Morphological investigations (atomic force microscopy and optical microscopy) reveal continuous deposited polymer thin films, and in the case of polyethylenimine a very low surface roughness of 1.2 nm (measured on a 40×40 μm2 area). It was found that only for a narrow range of laser fluences (i.e. 0.1–0.3 J/cm2 in the case of polyisobutylene) the chemical structure of the deposited polymer thin layers resembles to the native polymer. In addition, in the case of polyisobutylene it was shown that the irradiation at 355-nm wavelength produces deviations in the chemical structure of the deposited polymer, as compared to its bulk structure. Following the morphological and structural characterization, only a set of well established conditions was used for polymer deposition on the sensor structures. The surface acoustic wave resonators have been tested using the Network Analyzer before and after polymer deposition. The polymer coated surface acoustic wave resonator responses have been measured upon exposure to various concentrations of dimethylmethylphosphonate analyte. All sensors coated with different polymer layers (polyethylenimine, polyisobutylene, and polyepichlorhydrin) show a clear response to the dimethylmethylphosphonate vapor. The strongest signal is obtained for polyisobutylene, followed by polyethylenimine and polyepichlorhydrin. The results obtained indicate that matrix-assisted pulsed laser evaporation is potentially useful for the fabrication of polymer thin films to be used in applications including microsensor industry.

Detection of Explosive Vapors by Surface Acoustic Wave Sensors Containing Novel Siloxane Based Coatings

Surface acoustic wave (SAW) sensor was coated with a new chemoselective polymer to detect nitroaromatic explosives. Adsorption of the analyte influences the propagation of SAW and thus causes a shift in the resonant frequency of the SAW device. A novel azobenzene functionalized siloxane polymer was developed and applied to a surface acoustic wave (SAW) sensing device for the detection of explosive vapors such as 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT). The experimental setup used for evaluating the response of this polymers-coatings is described in the paper. Experimental results indicate that the viscoelastic properties of the polymer coating is fairly insensitive to the temperature changes occurring in our experiments, which is ideal for SAW sensing device. The PDMS coating is able to detect DNT and TNT vapors.

A comparative study of DRL-lift and lift on integrated polyisobutylene polymer matrices

This paper presents a comparative study of polymer pixel on sensors obtained by Laser Induced Forward Transfer (LIFT) assisted by a triazene polymer as Dynamic Release Layer (DRL). Polyisobutylene (PIB) was selected as model for chemoselective polymers which could be used as hydrogen-bond acidic polymer for vapor sensors. PIB films deposited on fused silica, respectively, on triazene polymer coated fused silica substrates were used as targets. Both targets were prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE). The parameters related to a regular, well-defined transfer were analyzed and compared for the substrates with and without the DRL. The morphological characterization of the transferred PIB was performed by Atomic Force Microscopy (AFM), Optical Microscopy, and Scanning Electron Microscopy (SEM). It was found that a minimal thickness of the dynamic release layer, i.e. 100 nm is required to protect the sensitive PIB polymer in a clean laser transfer process.

Waveguide micro-opto-electro-mechanical resonant chemical sensors

We demonstrate a silicon micro-opto-electro-mechanical sensor based on mass-loading of a chemo-selective polymer coated onto a microbridge. The sensor is probed optically using an on-chip waveguide Fabry-Pérot interferometer for high resolution displacement and resonant frequency measurement. The mechanical resonator is designed with paddles to simplify chemo-selective polymer deposition and to minimize any strain effects from the polymer during analyte sorption. Water vapor sensing experiments indicate mass-loading with minimum humidity detection of DeltaRH = 0.25% corresponding to a measured limit-of-detection of 68 parts-per-million. The sensor response time constant is 30 s with minimum frequency noise of 58 Hz at 149.4 kHz resonance. The measured mass-loading resolution is 4.6 picograms. We extract the chemo-selective polymer's partition coefficient and confirm that strong sorption and mass-loading occurs. Various device improvements are discussed, including scaling up to large single-chip sensor arrays, increasing mass-loading resolution by adjusting the device geometry, and using other chemo-selective polymers with larger partition coefficients. These improvements suggest parts-per-billion limit-of-detection levels for a variety of toxic chemicals.

Anionic alternating copolymerization of a bifunctional six‐membered lactone and glycidyl phenyl ether: Selective synthesis of a linear polyester having lactone moiety

AbstractAn imidazole‐initiated copolymerization of an aromatic bislactone, 10‐methyl‐2H,8H‐benzo[1,2‐b:5,4‐b′]bipyran‐2,8‐dione (1), and glycidyl phenyl ether (GPE) was investigated. In spite of the bifunctional nature of 1 that would potentially permit formation of networked and thus insoluble polymers upon its copolymerization, only one of the two lactone moieties of 1 exclusively underwent the copolymerization to give a linear polyester. Spectroscopic analysis of the polyester and its reductive scission into the corresponding fragment revealed that the polyester was formed by a 1:1 alternating copolymerization of GPE and the lactone moiety of 1. The other lactone in 1 that did not participate in the copolymerization was quantitatively incorporated into the side chain of the polyester as a reactive site, of which ring‐opening reactions by amine and alcohol as nucleophilic reagents allowed chemoselective polymer reactions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1661–1672, 2009

Synthesis and evaluation of a new polysiloxane as SAW sensor coatings for DMMP detection

Abstract A new polysiloxane material, polymethyl[3-(2-hydroxy)phenyl] siloxane (PMPS), was synthesized. The PMPS is a linear polysiloxane polymer functionalized with o -allyl phenol group. The chemoselective polymer was spin-coated on a 434 MHz surface acoustic wave (SAW) device for detection of dimethyl methylphosphonate (DMMP) vapor ranging from 5 to 40 ppm. It was found that the frequency shifts were linear to the vapor concentrations with a high sensitivity of 3 kHz/ppm. Fast response of 30 s and good reproducibility were achieved as well. The influence of humidity on the sensor response was also examined. The results showed that the sensitivity decreased about 1/2 when tested in 70% RH wet air than in dry nitrogen.

All-optical micromechanical chemical sensors

The authors describe experimental results from micromechanical resonators coated with a chemoselective polymer that detect chemical vapors from volatile organic compounds using all-optical interrogation. The shift in the resonant frequency of the gold microbeam is read out using photothermal actuation and microcavity interferometry. Response times of less than 5s are achieved for vapor concentrations as low as 60ppm using optical powers of a few megawatts.

Flexible carbon nanotube sensors for nerve agent simulants

Chemiresistor-based vapour sensors made from network films of single-walledcarbon nanotube (SWNT) bundles on flexible plastic substrates (polyethyleneterephthalate, PET) can be used to detect chemical warfare agent simulants for thenerve agents Sarin (diisopropyl methylphosphonate, DIMP) and Soman (dimethylmethylphosphonate, DMMP). Large, reproducible resistance changes (75–150%),are observed upon exposure to DIMP or DMMP vapours, and concentrations aslow as 25 ppm can be detected. Robust sensor response to simulant vapours isobserved even in the presence of large equilibrium concentrations of interferentvapours commonly found in battle-space environments, such as hexane, xylene andwater (10 000 ppm each), suggesting that both DIMP and DMMP vapours arecapable of selectively displacing other vapours from the walls of the SWNTs.Response to these interferent vapours can be effectively filtered out by using a2 µm thick barrier film of the chemoselective polymer polyisobutylene(PIB) on the SWNT surface. These network films are composed of a1–2 µm thick non-woven mesh of SWNT bundles (15–30 nm diameter), whose sensor response isqualitatively and quantitatively different from previous studies on individualSWNTs, or a network of individual SWNTs, suggesting that vapour sorptionat interbundle sites could be playing an important role. This study also showsthat the line patterning method used in device fabrication to obtain any desiredpattern of films of SWNTs on flexible substrates can be used to rapidly screensimulants at high concentrations before developing more complicated sensor systems.

Functionalized polysiloxane thin films deposited by matrix-assisted pulsed laser evaporation for advanced chemical sensor applications

Abstract High-quality thin films of fragile chemoselective polymers with precise and accurate thickness, density and chemical integrity are required for advanced chemical sensor applications. While these attributes are difficult to achieve by conventional methods, we have successfully demonstrated the matrix-assisted pulsed laser evaporation (MAPLE) deposition of thin films of especially synthesized fluoro-alcohol substituted carbo-polysiloxane polymer coatings. The quadrupled output of a Nd:YAG laser (265 nm) served as the laser source and depositions were done in a background pressure of N2. Using various solvents appropriate to solvate this polymer (e.g. tetrahydrofuran, acetone and chloroform) and varying the laser fluence, we optimized the deposition of high-quality thin films on 1 cm2 double-polished silicon substrates. The best solvent used as matrix was proved to be acetone. Under these conditions, the important functional groups were reproduced and observed by Fourier Transform Infrared Spectroscopy (FTIR) as compared to the drop cast films and the surface roughness was analysed using Atomic Force Microscopy (AFM) and found to be much smoother than conventional wet deposition techniques.

Combinatorial Synthesis of MUC1 Glycopeptides: Polymer Blotting Facilitates Chemical and Enzymatic Synthesis of Highly Complicated Mucin Glycopeptides

The chemoselective polymer blotting method allows for rapid and efficient synthesis of glycopeptides based on a "catch and release" strategy between solid-phase and water-soluble polymer supports. We have developed a heterobifunctional linker sensitive to glutamic acid specific protease (BLase). The general procedure consists of five steps, namely (i) the solid-phase synthesis of glycopeptide containing BLase sensitive linker, (ii) subsequent deprotections and the release of the glycopeptide from the resin, (iii) chemoselective blotting of the glycopeptide intermediates in the presence of water-soluble polymers with oxylamino functional groups, (iv) sugar elongations using glycosyltransferases, and (v) the release of target glycopeptides from the polymer platform by selective BLase promoted hydrolysis. The combined use of the solid-phase chemical syntheses of peptides and the enzymatic syntheses of carbohydrates on water-soluble polymers would greatly contribute to the production of complicated glycopeptide libraries, thereby enhancing applicative research. We report here a high-throughput synthetic system for the various types of MUC1 glycopeptides exhibiting a variety of sugar moieties. It is our belief that this concept will become part of the entrenched repertoire for the synthesis of biologically important glycopeptides on the basis of glycosyltransferase reactions in automated and combinatorial syntheses.

Nerve agent detection using networks of single-walled carbon nanotubes

We report the use of carbon nanotubes as a sensor for chemical nerve agents. Thin-film transistors constructed from random networks of single-walled carbon nanotubes were used to detect dimethyl methylphosphonate (DMMP), a simulant for the nerve agent sarin. These sensors are reversible and capable of detecting DMMP at sub-ppb concentration levels, and they are intrinsically selective against interferent signals from hydrocarbon vapors and humidity. We provide additional chemical specificity by the use of filters coated with chemoselective polymer films. These results indicate that the electronic detection of sub-ppb concentrations of nerve agents and potentially other chemical warfare agents is possible with simple-to-fabricate carbon nanotube devices.

Resonant infrared pulsed-laser deposition of a sorbent chemoselective polymer

Fluoropolyol, a sorbent chemoselective polymer, has been deposited as a thin film by resonant infrared pulsed laser deposition using a free electron laser operating at 2.90 μm, a wavelength resonant with the hydroxl stretch. A comparison of the infrared absorbance of the deposited film and starting material shows no evidence of chemical decomposition in the film. Gel permeation chromatography shows that the film and starting material have nearly the same molar mass. The results are particularly applicable to the fabrication of chemical and biological sensors. The concept of resonant pulsed laser deposition using intrinsic vibrational modes may have wide applicability for organic materials.

Rational materials design of sorbent coatings for explosives: applications with chemical sensors

A series of chemoselective polymers had been designed and synthesized to enhance the sorption properties of polymer coated chemical sensors for polynitroaromatic analytes. To evaluate the effectiveness of the chemoselective coatings, a polynitroaromatic vapor test bed was utilized to challenge polymer coated surface acoustic wave (SAW) devices with different explosive vapors. Dinitrotoluene detection limits were determined to be in the <100 parts per trillion ranges. ATR-FTIR studies were used to determine the nature of the polymer-polynitroaromatic analyte interactions, and confirm the presence of hydrogen-bonding between polymer pendant groups and the nitro functional groups of polynitroaromatic explosive materials.

A chemical sensor based on internal friction

This study demonstrates the detection of and differentiation between airborne chemicals using high resolution internal friction and frequency measurements. In essence, we determine the loss (1/ Q) per unit mass of analyte absorbed by a chemoselective polymer deposited on a resonator. We report the selectivity and sensitivity of this sensing technique for AT-cut quartz resonators coated with two different chemoselective polymers exposed to each of six different analytes. We also used spectra subtraction to extract the mechanical response changes of the thin film polymer coating from that of the coated resonators both with and without an analyte present.

The design of functionalized silicone polymers for chemical sensor detection of nitroaromatic compounds

The solubility properties of a series of nitroaromatic compounds have been determined and utilized with known linear solvation energy relationships to calculate their sorption properties in a series of chemoselective polymers. These measurements and results were used to design a series of novel chemoselective polymers to target polynitroaromatic compounds. The polymers have been evaluated as thin sorbent coatings on surface acoustic wave (SAW) devices for their vapor sorption and selectivity properties. The most promising materials tested, include siloxane polymers functionalized with acidic pendant groups that are complimentary in their solubility properties for nitroaromatic compounds. The most sensitive of the new polymers exhibit SAW sensor detection limits for nitrobenzene (NB) and 2,4-dinitrotoluene in the low parts per billion (ppb) and low parts per trillion (ppt) concentration range, respectively. Polymers with favorable physicochemical properties exhibit low water vapor sorption, and rapid signal kinetics for NB, reaching 90% of signal response in 4 s. Studies with an in situ infrared spectroscopy technique are used to determine the mechanism of interaction between nitroaromatic compounds and the chemoselective polymer.