Temperature-responsive fibers

Fig. 7.24 Temperature response of a fiber inline MZI fabricated by C02 laser irradiations...

Liquid crystalline polymers are important in the fabrication of lightweight, ultra-high-strength, and temperature-resistant fibers and Aims such as Dupont s Kevlar and Monsanto s X-500. The structural factors responsible for promoting the above classes of polymers will be discussed when we treat the structure of polymers. 

Figure 3.18 (a) Internal flaw responsible for fracture in a high temperature carbon fiber (b) Internal flaw responsible for fracture in a carbonized carbon fiber. Source Photomicrograph kindly supplied by Johnson JW. 

In this section, physical stimuli-responsive fibers will be introduced, which are composed of polymers responsive to temperature, light/UV, or electric/magnetic field, which enable on/off switching and reversible property changes of nanofibers. 

Miura N (1991) New-type calorimetric gas sensor using temperature characteristics of piezoelectric quartz crystal fitted with noble metal catalyst film. Sens Actuators B 5 211-217 Monz6n-Hemdndez D, Luna-Moreno D, Martfnez-Escobar D (2009) Fast response fiber optic hydrogen sensor based on palladium and gold nano-layers. Sens Actuators B 136 562-566 Mueller WM, Blackledge IP, Libowitz GG (1968) Metal hydrides. Academic, New York, NY Noh J-S, Lee JM, Lee W (2011) Low-dimensional palladium nanostmctures for fast and rehable hydrogen gas detection. Sensors 11 825-851... 

Another approach to produce temperature-responsive films is through hydrogen-bonded self-assembly [136]. Quinn and Caruso have demonstrated that the dye absorption and release capabihty of hydrogen-bonded PNIPAM/PAA multilayers was significantly enhanced at elevated temperatures [137]. In addition, temperature-controlled release of dyes from electrospun PAA/PAH nanofibers was obtained by depositing temperature-sensitive PAA/PNIPAM multilayers onto the fiber surfaces [138]. 

Surface prop>erties can be modified by thin layers of grafted polymers on a surface (not only flat substrates, but also colloidal particles, fibers, etc). These layers can be fabricated by grafring-from (as radical polymerization at the interface) and grafring-to (as tethering of the polymer chains from solution) methods. Grafted surfaces using smart temperature-responsive polymers can modulate cell adhesion and detachment properties in dependence on the temprerature. Cells adhere and proliferate on hydrophobic surfaces rather than hydrophilic ones. They tend to adhere to the surface with appropriate hydrophobidty. Polymer brush systems can be used to control adsorption mechanism, for example, protein adsorption or adsorption of nanopartides. 

Preliminary research has shown that Brillouin fiber-optic sensing systems provide a possible method to detect leaks and third-party intrusion on a pipeline over distances of 25 km or more. Their intrinsic response to both temperature and mechanical strain allows for the separation of these parameters and the detection of anomalies in the scan profiles. In addition, the same sensor could be integrated into the pipeline system to detect possible ground movement relative to fixed reference points. Limited test results on surface loads associated with the intrusion of vehicles and people on a pipeline have demonstrated the sensitivity of the system and its ability to discriminate loads at different soil depths. 

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