GB2447965A - Interpenetrating polymer network containing a nanoparticle for chemical sensing - Google Patents

Interpenetrating polymer network containing a nanoparticle for chemical sensing Download PDF

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Publication number
GB2447965A
GB2447965A GB0706199A GB0706199A GB2447965A GB 2447965 A GB2447965 A GB 2447965A GB 0706199 A GB0706199 A GB 0706199A GB 0706199 A GB0706199 A GB 0706199A GB 2447965 A GB2447965 A GB 2447965A
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network
nanoparticle
interpenetrating
polymer network
interpenetrating polymer
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GB2447965B (en
GB0706199D0 (en
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Saeed Rehman
Ihtesham Ur Rehman
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FIBERLOGIX Ltd
QUEEN MARY
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FIBERLOGIX Ltd
QUEEN MARY
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/75Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
    • G01N21/77Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
    • G01N21/7703Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator using reagent-clad optical fibres or optical waveguides
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B82NANOTECHNOLOGY
    • B82YSPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y15/00Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N31/00Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
    • G01N31/22Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
    • G01N31/223Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for investigating presence of specific gases or aerosols
    • G01N31/225Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators for investigating presence of specific gases or aerosols for oxygen, e.g. including dissolved oxygen

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  • Chemical & Material Sciences (AREA)
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  • Life Sciences & Earth Sciences (AREA)
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  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Molecular Biology (AREA)
  • Plasma & Fusion (AREA)
  • Biophysics (AREA)
  • Dispersion Chemistry (AREA)
  • Emergency Medicine (AREA)
  • Nanotechnology (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Investigating Or Analysing Materials By The Use Of Chemical Reactions (AREA)

Abstract

An interpenetrating polymer network of polyurethane and polymethyl methacrylate wherein said network is provided with a nanoparticle. The use of the interpenetrating polymer network as an optical waveguide is also described.

Description

* 2447965 A porous IPN polymer structure for use in chemical sensing
applications The present invention relates to improvements in chemical sensing for optical waveguides. In particular, the invention relates to improvements in fibre optical sensors which are used in chemical sensing.
In general, sensors that are intended to detect chemicals are electrical in nature. These electrical sensors are typically relatively large in size, and have a complex mode of operation. Further, they require a power supply close to the sensing location.
There is currently particular interest in gas sensors, especially oxygen and hydrogen sensors, as it is believed that these gases will be an important future energy source. Oxygen sensing has the further advantage of potential biomedical applications, e.g in chest medicine and intensive care.
It may be possible to improve the response time by using a porous structure. It is known that a greater surface area results in a faster reaction. Accordingly, shorter response times can be achieved by increasing the porosity of the cladding material.
Porous materials, as its name imply, are the solid materials containing pores. They can be classified into two types: open pores and close pores. The former means the pores are connected to the outside environment of the materials. They are important to the industry since it can offer a large surface I volume ratio and be used as filter and carrier for various applications such as catalyst and bioreactor.
The latter, in contrast, indicates that the pores are isolated from the outer environment of the materials. They are mainly used as heat and sound insulator.
An interpenetrating polymer network is a polymer network which comprises two or more polymer networks which are at least partially interlaced on a molecular scale but not covalently bonded to * each other and cannot be separated unless chemical bonds are broken. The properties of such materials are significantly different form the properties of corresponding co-polymers.
JPN's are extensively used in the development of novel plastic materials, and also in the medical
field.
According to a first aspect of the present invention there is provided an interpenetrating polymer network of polyurethane and polymethyl methacrylate wherein said network is provided with a nanoparticle.
I
The nanoparticle is typically selected to be a chemically responsive material. The nanoparticle can have a larger interaction by changing its shape or size, hence the surface area. The nanoparticle can be selected from the group comprising pyrene, palladium, titanium oxide, platinum or rhodium, indium oxide (1n203)-doped tin oxide (Sn02), Pd/Ag Alloy and functionalised metal nanoparticles The polymer network is typically in the form of an open porous network.
According to a second aspect of the present invention there is provided the use of the porous interpenetrating polymer network of the first aspect of the present invention in an optical waveguide.
The interpenetrating polymer network is typically used as part of the cladding of an optical waveguide. A suitable optical waveguide is an optical fibre.
The optical fibre is preferably used to detect the presence of a gaseous chemical. The gaseous chemical can be selected from the group comprising oxygen, hydrogen, carbon dioxide and carbon monoxide.
Preferred embodiments will now be described by way of example only, with reference to the accompanying Figures, in which: Figure 1 illustrates the design of a fibre optic sensor using the interpenetrating polymer network of the present invention; and Figure 2 illustrates the design of a fibre optic sensor using the interpenetrating polymer network of the present invention.
The IPNs of the present invention are made by impregnating/absorbing materials having a known affinity for gas sensing in polymeric matrix. Polyurethane/polymethylmethacrylate interpenetrating networks (PUIPMMA IPN) are synthesized by sequential IPN and simultaneous IPN.
In a sequential method PU, with different NCO/OH ratios, is synthesized by reacting isophorone diisocyanate with hydroxyl functional group of a caster oil, followed by immersion into a MIvIA solution. The resulting mixture is then radically polymerized with beazoyl peroxide initiator and ethylene glycol dimethacrylate crosslinker. Other soft segments of both the polyether and polyester type can used in the synthesis process. In addition other di-and tri-isocyanates can also be employed.
In a simultaneous method, polymers are synthesised simultaneously by thermal polymerisation and photopolymerization. In addition, radiation is useful in increasing the degree of the interpenetration.
Additional polymer networks based on PU and different acrylates, such as PMMA, poly(n-butyl acrylate) and PGMA can be synthesised.
A number of methods are available for synthesising a porous 1PN, such as solvent casting/particle leaching, fiber bonding, emulsion freeze-drying and supercritical fluids technology (gas forming) to form interconnect-porous structure. Each process will bring about different pore sizes.
The porosity of the porous material will be decided by the amount of the porogens, and the size of the pore is dependent on the size of the porogens. Pore size of 3O-3001tm and porosity of 20-50% have been reported with water-soluble porogens. In the case of waxy hydrocarbon porogens, 87% porosity and pore size of 1 00im have been demonstrated.
The interpenetrating polymer network of the present invention can be characterized using techniques which are well known to the man skilled in the art, e.g. FTIR, DSC, and other morphological techniques.
As far as the interconnected porous structure is concerned, the sensitivity of the fiber optics sensor can be maximized by ensuring that the diameter of the porous structure should be larger than the thickness of the impregnated or adsorbed nanoparticle. For example when the nanoparticle is selected to be a pyrene crystal, its presence will not block the diffusion of oxygen.
The formation of the interconnected porous structure and the nanoparticles impregnation process can be achieved simultaneously by either (1)gas forming or (2) solvent casting/particle leaching methods. The gas forming method is carried out using ammonium bicarbonate porogens. The solvent casting/particle leaching method utilizes sodium chloride as a water soluble porogen.
Alternatively waxy hydrocarbon porogens can be used.
The use of water soluble porogens involves the dissolution of polymers into non-polar solvents. The dissolved polymer is then cast into a mould or a petri dish with the introduction of the water-soluble porogens followed by the mold being placed in vacuum drier.
The use of waxy hydrocarbon porogens requires a different manufacturing process in which porogens are mixed with a dissolved polymer to form a paste in a mould followed by the waxy porogens being leached out first by the hydrocarbon solvents, Factors affecting the morphology of IPN include chemical compatibility of the ingredient polymer chain, interfacial tension, crosslink density of the networks, method of polymerization and the composition of the IPN structure. In terms of morphology, phase separation is commonly observed from the IPN network. The solubility parameters of the polymer are found to play the most important role in the phase separation. If the two ingredient polymers have closer solubility parameters, IPN will have smaller phase domain size than the 1PN whose ingredient polymers have solubility parameters apart from each other. The optical properties are further affected by the size of the phase domain. A polymer with high transparency usually indicates a small phase domain which has a minimal effect on the light propagating therein. The solubility parameters of PMMA and PU are very similar.
Pyrene which is a fluorescent material is physically immobilized in the porous PUIPMMA IPN by two different methods. The first method is done by physical immobilization of pyrene during the IPN synthesis and the second method is by using supercritical fluids.
The cladding material of a commercial optical waveguides such as optical fibre can be removed and replaced by the interconnected porous PU/PMMA interpenetrating polymer network. The bonding strength between the cladding and the fiber core is critical to the reliability of the sensor. The coating technique can have a significant impact on the bonding strength.
A cross section through an optical fibre suitable for use in the present invention is shown in figure 1.
The optical fibre 1 comprises a fibre core 2 surrounded by a cladding layer 3. The fibre 1 acts as a dielectric waveguide for optical signals passing along the fibre 1 and with an evanescent field or decaying field which extends into the cladding layer 3 from the fibre core 2. If a part of the cladding layer 3 is removed to form a recess 4 so that the evanescent field can be accessed, it is then possible to change the properties of the light passing along the fibre I by changing the conditions encountered by the exposed part of the evanescent field within the recess.
The characteristic of the light which is affected will depend on the precise characteristics of the optical fibre 1, the degree of exposure of the evanescent field and the changes made in the conditions experienced by the evanescent field. Typically the light level or the polarisation of light transmitted along the core or the amount of light reflected back along the fibre 1 will be changed.
Figures 1 and 2 illustrates a typical example of an optical fibre 1 which has a core 2 about 10 microns in diameter surrounded by a cladding layer 3 with a thickness of about 125 microns. When light passes along the fibre 1 the evanescent field will typically extend from the core 2 about I or 2 microns into the cladding layer 3.
This example is purely illustrative and use of these specific dimensions is not essential.
As shown in Figures 1 and 2, one or more recesses 4 are opened in the cladding layer 3 of the fibre 1, the recesses 4 having sufficient depth to expose the evanescent field of light passing along the fibre 1.
Preferably the recesses 4 in the cladding 3 of the fibre 1 are formed by laser micro machining to form recesses of a desired shape and size. However, other methods of removing cladding material to expose the evanescent field are known, for example grinding and polishing the optical fibre I. The use of laser micro machining is generally preferred in order to increase repeatability and yield and to allow recesses 4 with a defined shape and size to be provided. Laser micro machining allows a large number of small recesses 4 to be formed, increasing the sensitivity and versatility of the sensor.
Use of a laser micro machine method according to G240 705 5B is particularly preferred.
In order to cause a recess 4 to act as a chemical sensor responsive to the presence of a desired chemical the recess 4 is at least partially filled with a layer 5 of a chemically responsive material, as shown in figure 4. The chemically responsive material comprises a matrix of polymer material loaded or impregnated with nanoparticles formed of a material reactive to the presence of the chemical species desired to be sensed.
The refractive indexes of the polymer matrix and the nanoparticles and the loading quantity of the nanoparticles are selected so that the loaded polymer matrix forming the chemically responsive material has a bulk or average refractive index similar to or matching the refractive index of the cladding layer 3 of the optical fibre 1. When the chemical to be sensed by the sensor is present the nanoparticles react, changing the average refractive index of the chemically responsive material.
This change in refractive index effects the evanescent field of optical signals passing along the optical fibre 1, producing a change in the intensity or polarisation of the transmitted and/or reflected optical signals which can be detected in order to sense the presence of the chemical. If the starting refractive index of the polymer matrix is matched to the core of the optical fiber, when the refractive index of the loaded polymer matrix changes in response to the presence of the chemical to be detected, a large change in the optical signal transmitted in the fiber will be observed.
If the chemical sensors are distributed along the optical fibre, the location at which the chemical has been sensed, that is the location of the sensor detecting the chemical, can be determined. This can for example be carried out by known techniques such as optical time domain reflectometry (OTDR).
One possibility is to form sensors with different chemically responsive materials to detect different chemicals distributed along an optical fibre. By using OTDR to determine where a change in refractive index, polarisation or absorption has taken place, the reacting sensor, and thus the identity of the chemical being detected, can be determined.
With different impregnated chemicals within the polymer cladding, sensors for the different gases, such as oxygen, hydrogen and carbon dioxide can be manufactured. For example, palladium is a hydrogen sensitive metal which can react with hydrogen as much as 80 folds of its volume.
The application range of this fiber optics sensor can be expanded by adding a "specific substance" permeable membrane outside the cladding for the specific substance sensitive fiber optics sensor.

Claims (9)

  1. Claims I. An interpenetrating polymer network of polyurethane and
    polymethyl methacrylate wherein said network is provided with a nanoparticle.
  2. 2. An interpenetrating network as claimed in Claim I wherein the nanoparticle is in the form of a chemically responsive material.
  3. 3. An interpenetrating network as claimed in Claim 2 wherein the nanoparticle has a larger interaction surface area by changing its size or shape.
  4. 4. An interpenetrating network as claimed in any of the preceding Claims wherein the nanoparticle is selected from the group consisting of pyrene, palladium, titanium oxide, platinum or rhodium, indium oxide (1n203)-doped tin oxide (Sn02), PdIAg Alloy and functionalised metal nanoparticles.
  5. 5. An interpenetrating network as claimed in any of the preceding Claims wherein the polymer network is in the form of an open porous network.
  6. 6. The use of the interpenetrating polymer network of any of Claims 1-5 in an optical waveguide.
  7. 7. The use as claimed in Claim 6 wherein the interpenetrating polymer network is used as part of the cladding of the optical waveguide.
    8. The use as claimed in either Claim 6 or Claim 7 wherein the optical waveguide is an optical fibre.
  8. 8. The use as claimed in any of Claims 6 -8 wherein the optical fibre is used to detect the presence of a gaseous chemical.
  9. 9. The use as claimed in and of Claims 6-8 wherein the gaseous chemical is selected from the group comprising oxygen, hydrogen, carbon dioxide and carbon monoxide.
GB0706199A 2007-03-29 2007-03-29 A porous IPN polymer structure for use in chemical sensing applications Expired - Fee Related GB2447965B (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110505906A (en) * 2017-01-10 2019-11-26 得克萨斯州A&M大学系统 The uninanned platform of the acid mediated conjugation porous polymer network of methylsulphur

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106751738B (en) * 2016-11-18 2019-04-05 南昌航空大学 A kind of preparation method of high grade of transparency PMMA-PU gradient layer composite board

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020142477A1 (en) * 1999-05-10 2002-10-03 Lewis Nathan S. Spatiotemporal and geometric optimization of sensor arrays for detecting analytes fluids
WO2003025627A2 (en) * 2001-06-01 2003-03-27 Colorado State University Research Foundation Optical biosensor with enhanced activity retention for detection of halogenated organic compounds
US20050227242A1 (en) * 2004-04-13 2005-10-13 Sensors For Medicine And Science, Inc. Non-covalent immobilization of indicator molecules
US7176247B1 (en) * 2003-06-27 2007-02-13 The United States Of America As Represented By The Secretary Of The Army Interpenetrating polymer network

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020142477A1 (en) * 1999-05-10 2002-10-03 Lewis Nathan S. Spatiotemporal and geometric optimization of sensor arrays for detecting analytes fluids
WO2003025627A2 (en) * 2001-06-01 2003-03-27 Colorado State University Research Foundation Optical biosensor with enhanced activity retention for detection of halogenated organic compounds
US7176247B1 (en) * 2003-06-27 2007-02-13 The United States Of America As Represented By The Secretary Of The Army Interpenetrating polymer network
US20050227242A1 (en) * 2004-04-13 2005-10-13 Sensors For Medicine And Science, Inc. Non-covalent immobilization of indicator molecules

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110505906A (en) * 2017-01-10 2019-11-26 得克萨斯州A&M大学系统 The uninanned platform of the acid mediated conjugation porous polymer network of methylsulphur

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GB0706199D0 (en) 2007-05-09

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