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Temperature dependence polymer brushes

Thermally responsive polymers, such as poly( V-isopropyl acrylamide) (NI-PAm), have also been studied extensively for applications related to those previously discussed [112], De las Heras et al. described the synthesis and patterning of NIPAm brushes on SAMs and their subsequent performance during temperature-dependent adhesion assays of BSA and Streptococcus mutans (Fig. 7). The authors employed p.CP to pattern features of hydrophobic hexadecanethiol and backfilled the surface with an initiator-functionalized alkanethiol. Polymer brushes were grown via surface-initiated atom transfer radical polymerization (ATRP). FITC-BSA was then... [Pg.115]

Fig. 7 (a) Growth of temperature-dependent, patterned polymer brushes on SAMs on gold surfaces. Images show adhesion of (b) FITC-BSA after incubation at 37°C and rinse at 12°C (c) S. mutans after incubation at 4°C for 1 h and (d) S. mutans after incubation at 37°C for 1 h. Reproduced from [112] with permission. Copyright The Royal Society of Chemistry, 2005... [Pg.116]

On the basis of our experimental results presented so far, the overall viscoelastic behavior of these triblock copolymers shows an elasticity-dominance over the viscosity. After reaching the critical mass density, where the static elasticity es reaches the maximum, these triblock copolymers collapse into the subphase and form hydrated brushes and these anchored brushes may be responsible for the result that the surface viscosities drop to around the 0 value at r. A distinctive difference between two types of polymers, sample I (PEO-PPO-PEO) and sample II (PPO-PEO-PPO), is the temperature dependence of r where both static elasticity and dilational viscosity show kinds of transitions. V of sample I increases with increasing temperature while that of sample II does not change with temperature. [Pg.103]

There is a host of other intriguing phenomena associated with the structure and dynamics of stars, which we only list here. The inhomogeneous monomer density distribution in Fig. 2 is responsible for temperature and/or solvency variation in analogy to polymer brushes attached on a flat solid surface [198]. In fact, multiarm star solutions display a reversible thermoresponsive vitrification (see also Sect. 5) which, in contrast to polymer solutions, occurs upon heating rather than on cooling [199]. Another effect is the organization of multiarm stars in filaments induced by weak laser light due to action of electrostrictive forces [200]. This effect was recently attributed [201] to local concentration fluctuations which provide localized-intensity dependent refractive index variations. Hence, the structure factor speciflc to the particular material plays a crucial role in the pattern formation. [Pg.25]

Xu and Liu recently reported the syntheses of the well-defined 7-arm and 21-arm PiPAAm stars with a P-cyclodextrin core [278, 568] and presented a thorough analysis of the literature on thermoresponsive stars and polymer brushes tethered to curved surfaces, such as latex particles [279, 280, 569], gold nanoparticles [282] and microgels [570], A unique feature of these architectures is that they form a densely packed spherical core and a less-dense outer shell [159]. As a result of such a non-uniform density distribution, two temperature-induced phase transitions have been observed experimentally in several systems based on PiPAAm [279, 280, 282, 568, 569], One transition has been ascribed to the phase transition of the inner segments of PiPAAm, whereas the other transition, which is concentration dependent, was assigned to the collapse of the outer PiPAAm segments [282],... [Pg.72]

Jia, H., Wildes, A., Titmuss, S. (2011). Structure of pH-responsive polymer brushes grown at the gold-water interface dependence on grafting density and temperature. Macromolecules, 45, 305-312. [Pg.61]

However, in a series of publications Ito et al. [7,23,24,26] have shown that polymer brush-decorated membranes offer a much faster response while depending on the mechanical properties of the porous membrane, they can be more mechanically robust. In these publications it was also demonstrated that different types of external stimuli, such as variation of pH, temperature, solvent quality, and ultraviolet irradiation, might be used for the control of solvent permeation through the membranes. [Pg.128]

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. [Pg.404]


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See also in sourсe #XX -- [ Pg.370 , Pg.371 , Pg.372 ]




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