Polymer Gel Systems Research Articles

MO‐B‐BRB‐02: 3D Dosimetry in the Clinic: IMRT Technique Validation in Sweden

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

MO‐B‐BRB‐00: Three Dimensional Dosimetry

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

MO‐B‐BRB‐04: 3D Dosimetry in End‐To‐End Dosimetry QA

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

MO‐B‐BRB‐03: 3D Dosimetry in the Clinic: Validating Special Techniques

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

MO‐B‐BRB‐01: 3D Dosimetry in the Clinic: Background and Motivation

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

Stimuli‐responsive molecularly imprinted hybrid polymer gel as a potential system for controlled release

ABSTRACTThe purpose of this study is to develop a stimuli‐responsive hybrid polymer gel system with an improved mechanical stability as a controlled drug delivery carrier that can undergo phase transition by the stimulation of ethanol–water mixture. For this aim, trimethoxysilane terminated poly(propylene glycol) by coupling of 3‐isocyanatopropyl‐triethoxysilane with the hydroxyl end groups of poly(propylene glycol) through urethane bonds was synthesized. Hybrid polymer gels prepared in the presence of tryptophan (Trp), as a model of drug, were characterized and gelation time of polymer network was obtained by monitoring the fluorescence emission of Trp in pre‐gel solution. Swelling, solvent uptake and release kinetic of polymer gels were evaluated depending on time. The diffusional exponents (n) and diffusion constants (k) of each gel were calculated by using the swelling kinetic data. The effect of precursors as a monomer on Trp release profile was analyzed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42913.

Electrophoretic mobility of semi-flexible double-stranded DNA in defect-controlled polymer networks: Mechanism investigation and role of structural parameters.

Our previous studies have reported an empirical model, which explains the electrophoretic mobility (μ) of double-stranded DNA (dsDNA) as a combination of a basic migration term (Rouse-like or reptation) and entropy loss term in polymer gels with ideal network structure. However, this case is of exception, considering a large amount of heterogeneity in the conventional polymer gels. In this study, we systematically tune the heterogeneity in the polymer gels and study the migration of dsDNA in these gels. Our experimental data well agree with the model found for ideal networks. The basic migration mechanism (Rouse-like or reptation) persists perfectly in the conventional heterogeneous polymer gel system, while the entropy loss term continuously changes with increase in the heterogeneity. Furthermore, we found that in the limit where dsDNA is shorter than dsDNA persistence length, the entropy loss term may be related to the collisional motions between DNA fragments and the cross-links.

High‐temperature‐resistant polymer gel system with metal–organic mixed cross‐linking agents

ABSTRACTA high‐temperature (200°C)‐resistant polymer gel system was developed from partially hydrolyzed polyacrylamide (HPAM), chromium lactate (CrL), and water‐soluble phenol/formaldehyde resin (WPF) mixed cross‐linkers. Rheological measurements indicated that the gelation process of the gel system could be divided into four successive steps: induction, first cross‐linking with metal cross‐linker, secondary cross‐linking with organic cross‐linker, and stabilization. Effects of various parameters that affect the gelation time and gel strength including polymer concentration, cross‐linker concentration, salinity, pH, and the gelation temperature were evaluated. Gelant formulated with 0.5 wt % HPAM, 0.1 wt % CrL, and 0.9 wt % WPF and treated at 80°C for 48 h showed sufficient gelation time, high rigidity, and good thermal stability. Morphology observation by scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that the gel had compact network microstructure. A cross‐linking mechanism for the gel system was proposed based on the gelation process and experimental results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 42261.

True 3D chemical dosimetry (gels, plastics): Development and clinical role

Since the introduction of volumetric chemical dosimetry with Fricke gel dosimeters in the 1980s, three-dimensional (3D) dosimetry has been a promising technique for the clinic, since it provides a unique methodology for 3D dose measurement of the complex conformal dose distributions achieved by modern techniques such as Intensity Modulated and Volumetric Arc Radiation Therapy. In the last decade, the potential for improved clinical applicability has been advanced by the development of improved 3D dosimeters such as normoxic polymer gel systems, radiochromic plastics (such as PRESAGE) and, recently, newer radiochromic gel dosimeters. Some of these new 3D dosimetry systems were enabled by the availability of optical computed tomography imaging systems for fast dose readout. However, despite its promise, true 3D dosimetry is still not widely practiced in the community. Its use has been confined primarily to select centres of expertise and to specialised quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. In this paper I review some of the current 3D chemical dosimeters available, discuss the requirements for their use and briefly review the roles that these systems can provide to complement the other dose delivery validation approaches available in the clinic. I conclude by describing two roles that may be uniquely served by 3D chemical dosimetry in end-to-end process testing and validation in the complex environment coming into play with the development of Image Guided Adaptive Radiation Therapy.

Novel Rigid-Setting, Temperature-Activated Material Stops Loss and Unwanted Fluids

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 24417, ’A Novel Temperature-Activated, Rigid-Setting Material: Case Histories for Drilling and Conformance Offshore Applications,’ by J. Vasquez, SPE, Halliburton, prepared for the 2013 Offshore Technology Conference Brasil, Rio de Janeiro, 29-31 October. The paper has not been peer reviewed. This paper discusses a rigid-setting- fluid (RSF) system that has proved successful for curing severe dynamic and static losses, pumping treatments through the drillstring bottomhole assembly (BHA) (no trip out required), because of its highly controllable fast-setting properties. In addition to drilling applications, this system has also been used to shut off undesired fluid production during offshore workover interventions in extreme cases where conventional cement slurries or polymer-gel systems have yielded little success. Introduction Excessive water production from hydrocarbon-producing wells is one of the more serious problems in the oil industry. Water tends to become the dominant produced fluid as hydrocarbon fields mature. Unwanted water production can affect well economics adversely because of water-disposal costs, environmental issues, and reduced hydrocarbon production. Other problems can develop as a result of the undesired water production, including sand production, scale, and corrosion. Water-production problems assume various forms: leaks in casing, producing tubing, or packers; flow behind casing; water coning (or water cresting in horizontal wells); or direct communication from the injector to the producer through high- permeability streaks or natural or induced fractures. Several techniques for controlling water production have been attempted, including mechanical and chemical treatments or combinations of both. This paper describes an innovative temperature-activated RSF system used for water and gas shutoff in near- wellbore (NWB)_applications. Another problem discussed in this paper is severe lost circulation while drilling. Uncontrolled losses to the formation represent a high-cost event during drilling stages, especially in offshore environments. These losses can be classified according to their severity: loss of circulation by filtration (1 to 10 bbl/hr), partial loss (10 to 500 bbl/hr), and total loss (500 bbl/hr or greater). Conventional lost-circulation materials (LCMs) used to control losses include bridging agents, gelling agents, or cementing-type materials. Most of the time, cementing-type materials are left as the final option because they require pulling the drillpipe out of hole and running with a cement stinger, resulting in significant additional cost to the drilling stage. On the contrary, even though most of the bridging and gelling LCMs can be pumped through the BHA, most of the time, they are not suited for high-rate losses. While the discussed RSF was originally developed for conformance applications, its chemical and mechanical properties provide a unique solution for treating severe cases of lost circulation— in particular, those related to natural or induced fractures—while pumping the treatment through the BHA.

Identification and selection of a stable gel polymer to control or reduce water production in gas condensate fields

The existence of water in hydrocarbon reservoirs damages the wells. In many cases, it leads to shut off the wells and decreases the gas production efficiency. For example, one of the problems of fractured gas wells is unwanted water invasion to gas production areas through the existing fracture in the reservoirs. This would increase the water production and decrease the gas production efficiency. As well, increasing of water/gas production ratio will increase the total operational costs due to water separation from the gas flow, corrosion of inside and outside well facilities and hydrate formation. Hence, prevention of water production in gas wells can boost the gas production economy. Generally, some mechanical and chemical methods exist to control unwanted water. One of the most effective methods to control and prevent of water production in hydrocarbon reservoirs is gel polymer method. The gel polymer is a chemical method with high efficiency and low cost. This work is concerned with producing a stable and suitable gel polymer (HPAM–Cr (III) gel system) to control and remove water in the gas condensate fields. The important parameters in the gel construction such as the polymer and cross-linker concentrations, pH of solution and also the effect of different additives have been examined and optimized at four temperatures of 30, 60, 80 and 100 °C. The effect of gel polymer on the absolute and relative permeabilities of two different cores for water and gas condensate fluids has been investigated. The results show that prepared gel polymer results in decreasing the water relative permeability, while increases the gas condensate relative permeability.

An experimental study of silicate–polymer gel systems to seal shallow water flow and lost circulation zones in top hole drilling

Abstract Shallow water and lost circulation are frequently encountered problems during drilling top holes of oil and gas wells. Plenty of methods have been applied to overcome these problems. Among these methods, silicate based gels are one of the oldest. For this study, Sodium-Silicate based gel system is investigated experimentally and several aspects of the system are improved for efficient field applications. This improved gel system is deliberately delayed, multi-component system to be mixed as a uniform liquid at the surface facilities but desired to form gel structure where it is placed in the well. Gel slurries are composed of distilled water, Sodium-Silicate solution, polymer solution, lost circulation materials, weighting agent and organic initiator (initiating the gelation). In this study, effect of these components on gel time, gel quality and gel strength at room temperature is investigated as a function of their concentration. In order to compare gelation time of different compositions, a new, easy and consistent gel time determination method is developed. Being based on vortex closure time, the method can be followed easily even by basic rig laboratories. Another new method is introduced to monitor long term gelation process by measuring turbidity (NTU) of the mixtures and plotting NTU versus time curves. In addition, unique observation codes are defined to compare the gel qualities of different compositions. For gel time and quality experiments, Sodium-Silicate concentrations from 3.5% to 15% by weight in the mixture were investigated and the concentrations range of 7.5–10% were found as applicable. It is determined that, gel time is getting higher as silicate–initiator ratio (SIR) increases for these optimum concentrations. The system is improved by addition of two different polymer solutions. These polymers not only improve the elasticity of the final gels but also provide sufficient viscosity to keep weighting agent and/or lost circulation materials (LCM) in suspension. In addition, viscosity development curves obtained from rotational viscometer at various constant shear rates indicated that, gelation is accelerated by applied shear. Furthermore, HTHP filter press cell was modified by manufacturing new bottom cap with 1 mm diameter hole in center to determine the extrusion pressures of the gels and it was found that, extrusion pressure can be increased by the addition of fibrous type lost circulation materials.

In Situ Gelation Study of Organically Crosslinked Polymer Gel System for Profile Modification Jobs

The crosslinked polymer gel systems are used in profile modification jobs to recover additional oil from matured oil fields where natural or induced fractures and fracture network, vertical permeability variations and channeling are the main hurdles during water flooding operations. In this work, crosslinked polymer gel solutions were prepared using partially hydrolyzed polyacrylamide polymer, hexamine and hydroquinone crosslinkers in the brine solution. These gel solutions were injected in the sand packs and kept in the oven at various ranges of temperature to meet the in situ reservoir conditions of the Indian oil fields. After complete gelation, the reduction in permeability of the sand packs was determined using brine flooding. The experimental investigation furnishes that the permeability reduction and residual resistance factor of the sand pack increases with increase in the polymer and crosslinker concentrations as well as temperature. It shows the potential of this crosslinked polymer gel system for high temperature and high- pressure wells.

Investigation of Preparation and Mechanisms of a Dispersed Particle Gel Formed from a Polymer Gel at Room Temperature

A dispersed particle gel (DPG) was successfully prepared from a polymer gel at room temperature. The polymer gel system, morphology, viscosity changes, size distribution, and zeta potential of DPG particles were investigated. The results showed that zirconium gel systems with different strengths can be cross-linked within 2.5 h at low temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) results showed that the particles were polygonal particles with nano-size distribution. According to the viscosity changes, the whole preparation process can be divided into two major stages: the bulk gel cross-linking reaction period and the DPG particle preparation period. A polymer gel with a 3-dimensional network was formed in the bulk gel cross-linking reaction period whereas shearing force and frictional force were the main driving forces for the preparation of DPG particles, and thus affected the morphology of DPG particles. High shearing force and frictional force reduced the particle size distribution, and then decreased the zeta potential (absolute value). The whole preparation process could be completed within 3 h at room temperature. It could be an efficient and energy-saving technology for preparation of DPG particles.

Investigating the Effect of Several Parameters on the Gelation Behavior of Partially Hydrolyzed Polyacrylamide–Hexamine–Hydroquinone Gels

The polymer gel systems are mostly used for the control of excessive water production during enhanced oil recovery operations in mature oil fields. However, these polymer gels are not stable in the high-temperature and high-salinity reservoir. Keeping these in mind, an attempt was made to investigate the effect of several parameters on the gelation time of polymer gels for its suitable application in the oil fields. In this paper, a polymer gel comprised of partially hydrolyzed polyacrylamide as a water-soluble polymer and hydroquinone and hexamine as organic cross-linking agents of low toxicity was prepared to control excessive water production. The effect of various parameters such as polymer and cross-linker concentrations, temperature, pH, and salinity on the gelation time and gel strength was evaluated using the bottle testing method, and variations in the performance of the polymer system were analyzed under different gel compositions and environmental conditions.

Mechanochromic Photonic Gels

Polymer gels are remarkable materials with physical structures that can adapt significantly and quite rapidly with changes in the local environment, such as temperature, light intensity, electrochemistry, and mechanical force. An interesting phenomenon observed in certain polymer gel systems is mechanochromism - a change in color due to a mechanical deformation. Mechanochromic photonic gels are periodically structured gels engineered with a photonic stopband that can be tuned by mechanical forces to reflect specific colors. These materials have potential as mechanochromic sensors because both the mechanical and optical properties are highly tailorable via incorporation of diluents, solvents, nanoparticles, or polymers, or the application of stimuli such as temperature, pH, or electric or strain fields. Recent advances in photonic gels that display strain-dependent optical properties are discussed. In particular, this discussion focuses primarily on polymer-based photonic gels that are directly or indirectly fabricated via self-assembly, as these materials are promising soft material platforms for scalable mechanochromic sensors.

ChemInform Abstract: Coordination Polymer Gels with Important Environmental and Biological Applications

AbstractReview: 45 refs.

Dosimetric characteristics of a new polymer gel and their dependence on post-preparation and post-irradiation time: Effect on X-ray beam profile measurements

The aim of this study is to dosimetrically characterize a new MRI based polymer gel system and to evaluate its usefulness in clinical practice just in terms of beam profile measurements.Normoxic N-vinylpyrrolidone based polymer gel (VIPET) phantoms were produced and used in order to perform three main sets of experiments: a) dose–response evaluation and reproducibility experiments, b) experiments for the evaluation of sensitivity of dose characteristics on ‘gel manufacture – irradiation’ time interval and c) experiments for the evaluation of sensitivity of dose characteristics on ‘irradiation – MRscanning’ time interval. It has been shown that this gel system can be used in a wide dose-range of 0–60 Gy. It exhibits a linear dose–response in the dose-range of 2–35 Gy. Following the proposed manufacturing method the dose–response characteristics are reproducible. Moreover, it seems that the optimum ‘gel manufacturing – irradiation’ time interval is 1 day. However, a ‘gel manufacturing – irradiation’ time interval up to ∼1 week can be safely used. The optimum ‘irradiation – MRscanning’ time interval in terms of dose–response sensitivity and dose resolution can be reliably ranged from 1 day to 3 weeks. Finally, X-ray beam profile gel-measurements were performed and found to be in satisfying agreement with corresponding small sensitive volume ion chamber measurements. VIPET gel dosimeters preserved the spatial integrity of the dose distribution during a time period of 50 days post-irradiation. The studied gel system can be safely used in clinical practice within the practical limitations found and described in this work.

Rheological study of partially hydrolyzed polyacrylamide-hexamine-pyrocatechol gel system

Background: The cross-linked polymer gels exhibit non-Newtonian rheological behavior which can be described well by the different types of rheological models. This study investigates the onset of gelation behavior of partially hydrolyzed polyacrylamide-hexamine-pyrocatechol polymer gel system which may be used to control excessive water production in the oil fields. Rheological measurements of this system have been performed at different time intervals and pH at 90°C. Attempts have been made to validate the onset of gelation behavior with Bingham plastic, Herschel-Bulkley, Mizrahi-Berk, and Robertson-Stiff model. Results: It was observed that the developed polymer gel system under the present study has better agreement with the Robertson-Stiff model. Conclusions: The viscosity of cross-linked polymer gel solution increases with temperature with the passage of time. This increased viscosity leads to gel formation which in turn behaves as flow diverting agent or blocking agent for controlling excessive water production in the oil fields.

Coordination polymer gels with important environmental and biological applications

Coordination Polymer Gels (CPGs) constitute a subset of solid-like metal ion and bridging organic ligand structures (similar to metal-organic frameworks) that form multi-dimensional networks through a trapped solvent as a result of non-covalent interactions. While physical properties of these gels are similar to conventional high molecular weight organic polymer gels, coordination polymer gel systems are often fully reversible and can be assembled and disassembled in the presence of additional energy (heat, sonication, shaking) to give a solution of solvated gelators. Compared to gels resulting from purely organic self-assembled low molecular weight gelators, metal ions incorporated into the fibrilar networks spanning the bulk solvent can impart CPGs with added functionalities. The solid/liquid nature of the gels allows for species to migrate through the gel system and interact with metals, ligands, and the solvent. Chemosensing, catalysis, fluorescence, and drug-delivery applications are some of the many potential uses for these dynamic systems, taking advantage of the metal ion's coordination, the organic polydentate ligand's orientation and functionality, or a combination of these properties. By fine tuning these systems through metal ion and ligand selection and by directing self-assembly with external stimuli the rational synthesis of practical systems can be envisaged.