Environmentally sensitive polymers

Ista LK, Perez-Luna VH, Lopez GP (1999) Surface-grafted, environmentally sensitive polymers for biofilm release. Appl Environ Microbiol 65 1603-1609... 

Environmentally Sensitive Polymers as Biosensors The Glucose-Sensitive Membrane... 

The design of a polymer-based system requires understanding both the steady state and transient behavior in response to the substrate or analyte of interest. For sensor applications, this information is obtained during the operation of the sensor. However, for other applications of environmentally sensitive polymers, such as drag delivery systems, the polymer response to the substrate/analyte is not usually studied directly. Our work with the pAAm/GO/PR system illustrates the usefulness of an in situ probe to measure what governs the membrane s performance in response to the substrate/analyte and how to analyze it. We continue to use this valuable information in the further... 

The synthesis of a bilayer, e.g. of an environmentally sensitive polymer and of a non-sensitive polymer with special properties (e.g. biocompatibility), is possible by coating a low cross-linked polymer layer with a second polymer and applying an additional irradiation step (Hegewald 2004). 

The membrane with the nanometer-sized holes can be used as template of metallic replicas. The holes are filled up with some metal atoms by electrolysis in a galvanic cell, and after deposition, the membrane is removed mechanically or by a suitable solvent. In these ways, little rods with a few pm length and few times 10 nm diameters are produced (Tagawa et al. 2004 Coqueret 2008). By grafting environmental sensitive polymers on the surface of the holes, the permeability of the membrane can be regulated by external signal (temperature, pH, etc.). The operation of such systems may mimic, the operation of biological membranes. 

Phase-sensitive smart (stimuli responsive, surroxmding environmentally sensitive) polymers offer the development of a controlled delivery system that can deliver the protein and peptides in stable and bioactive form in a controlled manner. Compared to other systems, phase-sensitive polymeric systems have advantages such as low cost, ease of manufacture, high protein and peptides loading capacity, less traumatic manufacturing conditions and the major advantage of phase-sensitive polymeric systems is the lyso-zymal enzyme release. This type of phase-sensitive polymeric system was prepared by incorporating lysozyme enzyme to poly(D,L-lactic acid) (PLA)-triacetin solutions [61]. 

Stimuli-sensitive or smart polymeric systems are defined as the polymers that might rise above dramatic property changes replying to minute changes in the environment [50]. The effect of different stimuli on environmental sensitive polymers (Figure 9.35) has been widely studied, and among these temperature is the most investigated stimulus since it is directly related to the human body [51]. 

There has been interest in smart polymers for many decades. Currently, a great deal of effort is being dedicated to developing environmentally sensitive polymers for the fabrication of new smart materials for use in the most advanced and sophisticated medical devices (Ravichandran et al, 2012 Roy et a/., 2010). This section and the following one deal with the most relevant types of smart polymers in terms of stimuli-responsive behaviour and structural properties, including new technologies for the synthesis of macromolecules that are able to form highly diversified structures. 

Recently, different authors proposed the blend of soy protein with environmentally sensitive polymers to synthesize composite materials with intelligent features, which may result in new potential applications in the biomedical and pharmaceutical fields. Li et al. report the synthesis and self-assembly behavior in aqueous solution of thermally responsive graft copolymer (SPl-g-p(iV-isopropylacrylamide]] of soy protein isolate and N-isopropylacrylamide in aqueous solution by using ammonium persulfate as the initiator and mercaptoacetic acid as the protein unfolding agent (Li et al., 2010]. Alternatively, temperature-sensitive interpenetrating polymer network hydrogels based on... 

The need for drug defivery systems to improve safety, efhcacy and patient compliance is well estabfished. There exist various drag delivery systems such as microspheres, nano particles, as well as environmentally sensitive systems [1-3]. Thermosensitive polymers are a subset of environmentally sensitive polymers which undergo a phase transition (sol-gel) when subjected to a change in temperature. 

Ozonc-rcsjstant elastomers which have no unsaturation are an exceUent choice when their physical properties suit the appHcation, for example, polyacrylates, polysulfides, siHcones, polyesters, and chlorosulfonated polyethylene (38). Such polymers are also used where high ozone concentrations are encountered. Elastomers with pendant, but not backbone, unsaturation are likewise ozone-resistant. Elastomers of this type are the ethylene—propylene—diene (EPDM) mbbers, which possess a weathering resistance that is not dependent on environmentally sensitive stabilizers. Other elastomers, such as butyl mbber (HR) with low double-bond content, are fairly resistant to ozone. As unsaturation increases, ozone resistance decreases. Chloroprene mbber (CR) is also quite ozone-resistant. 

Another class of environmentally sensitive materials that are being targeted for use in drug delivery applications is thermally sensitive polymers. This type of hydrogel exhibits temperature-sensitive swelling behavior... 

An attractive alternative to organic fluorophores in formulated polymeric sensor films for chemical detection is to use inorganic luminescent materials. Semiconductor nanocrystals have a dramatically improved photostability and are attractive as luminescent labels.1415 However, some nanocrystals also exhibit photoluminescence (PL) that is sensitive to the local environment. For example, it was observed that PL of CdSe nanocrystals incorporated into polymer thin films responded reversibly to different gases.16 Because in sensing applications nanomaterials bring previously unavailable capabilities1719 and unexpected results,20 23 we explored the environmental sensitivity of semiconductor nanocrystals upon their incorporation in different rationally selected polymeric matrices.24 26... 

The sensitivity of these sensors was defined as a signal change upon exposure to the known concentrations of vapors. Sensitivity of the 2.8-nm CdSe nanocrystals was 0.8 PL counts/Torr of methanol with almost no detectable sensitivity to toluene. The sensitivity of the 5.6-nm CdSe nanocrystals was 2.9 PL counts/Torr of methanol and 8.8PL counts/Torr of toluene. Although this environmental sensitivity was compatible with earlier reported sensors based on polished or etched bulk CdSe semiconductor crystals3940 and polymer-nanocrystals composites,16 the sensor reported here had a more selective response to polar and nonpolar vapors due to the multiwavelength PL from different-size nanocrystals incorporated into the polymer film. The response and recovery kinetics of PL from the 2.8-nm nanocrystals in PMM A upon exposure to methanol were very fast (<0.5 min). However, 5.6-nm nanocrystals in the same sensor film exhibited a much longer response and recovery times upon interactions with methanol, 4 and 20min, respectively. The 5.6-nm nanocrystals had 4-min response and 0.5-min recovery times upon interactions with toluene. 

Since any sample of polymer is characterised by a distribution of molecular weights and the fluorescence of a chromophore is in principle environmentally sensitive, even for non-interacting chromophores it would not be surprising if a distribution of decay... 

HPLC is a versatile technique applicable to diversified analytes, including labile molecules, ions, organic, and biopolymers. This chapter provides an overview of HPLC applications for the analysis of food, environmental, chemical, polymer, ion-chromatography, and life science samples. In food analysis, HPLC is widely used in product research, quality control, nutritional labeling, and residual testing of contaminants. In environmental testing, HPLC is excellent for the sensitive and specific detection of labile and nonvolatile pollutants... 

Seal BL, Panitch A (2003) Physical polymer matrices based on affinity interactions between peptides and polysaccharides. Biomacromolecules 4 1572-1582 Seal BL, Panitch A (2006) Viscoelastic behavior of environmentally sensitive biomimetic polymer matrices. Macromolecules 39 2268-2274... 

Measurement procedures using solutions in standard cuvettes are well developed. Some condensed phase samples such as large crystals and polymer films are relatively robust and easily mounted. Two areas of interest which have led to innovation are in the mounting of small, environmentally sensitive, single crystals and in the sample cells used for frozen glasses, particularly those having a substantial aqueous phase, such as proteins. 

The results also showed that the amount of absorbed NMP, or for that matter any airborne molecular base, depends on the solubility parameter of the polymer, on the nature of the contaminant, and on the Tg of the polymer. This was a remarkable result because it suggested that the environmental sensitivity of a resist polymer could be controlled by merely changing the Tg or the solubility parameter of the resist polymer. A verification of this result was obtained when the environmental stability of two polymers synthesized from two different isomers of BOCST monomers—the 3-BOCST and the 5-BOCST isomers—were found to have their environmental stability very well correlated with their Tg. The polymer with the significantly lower 7g—the 3- BOCST isomer—showed the least sensitivity to exposure to low levels of NMP. 

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