Polymers hydrophobic recovery

Bar, G., Delineau, L., Hafele, A. and Whangbo, M.H., Investigation of the stiffness change in, the indentation force and the hydrophobic recovery of plasma-oxidized polydimethyl-siloxane surfaces by tapping mode atomic force microscopy. Polymer, 42(8), 3627-3632 (2001). 

The surface modification is applied on hydrophobic polymers in this case, and the complication due to change of bulk phase due to water immersion is small. The decay of hydrophilic characteristics or hydrophobic recovery is similar to that occurring in air. 

Mortazavi M, Nosonovsky M. A model for diffusion-driven hydrophobic recovery in plasma-treated polymers. Appl Surf Sci 2012 258(18) 6876—83. 

Polymer surface restructuring has become a topic of considerable interest in recent years. It is of particular interest in efforts to increase the surface energy of relatively hydrophobic materials including silicone polymers. This can give benefits such as improved adhesion, better wettability, etc. but such efforts are often frustrated by a progressive hydrophobic recovery once the treatment ceases. The two most important areas of this type in the organosilicon polymer field are plasma treatment and corona discharge treatment. These two treatments are closely related. The former is often used to improve adhesion of... 

A wide variety of analytical techniques has been applied to shed light on the mechani sm of this hydrophobic recovery process including XPS, ATR - FTIR, GPC, SIMS, DMA, SEM, and contact angle. Our experience and that of others (for example, Triolo and Andrade °) is that the combination of XPS, SEM, and contact angle is a powerful surface analytical strategy for silicone polymer surfaces. We believe that many aspects of the preceding list of possible mechanisms are involved in this complex phenomenon and also that it is impossible to generalize as some silicone polymer systems behave quite differently to others. 

UV irradiation and plasma treatment. However, it has been observed that the water contact angle of the treated polymer surfaces increases gradually with time, thereby making them hydrophobic and less biocompatible. The phenomenon is called hydrophobic recovery of polymeric biomaterials and is being addressed in detail [36]. 

Meincken, M. Berhane, T. A. Mallon, P. E., Tracking the Hydrophobic Recovery of PDMS Compounds Using the Adhesive Force Determined AFM Force Distance Measurements. Polymer 2005,46, 203-208. 

Guimond S, Wertheimer MR. Surface degradation and hydrophobic recovery of polyolefins treated by air corona and nitrogen atmospheric pressure glow discharge. J Appl Polym Sci 2004 94 1291-303. 

V. Jokinen, P. Suvanto, and S. Franssila, Oxygen and nitrogen plasma hydrophilization and hydrophobic recovery of polymers. Biomicrofluidics, 6 (1), 016501-016501-10, 2012. 

An analogous phenomenon is the hydrophobicity recovery that occurs when a surface-oxidized polymer is stored in air. For instance, the 0/C concentration ratio was 0.01, 0.26, 0.25, 0.18 and the water contact angle was 96, 36, 50, 65°, respectively, for PS, and for plasma-oxidized PS analyzed within 24 h, analyzed... 

Time-dependent or relaxation phenomena [113] may also occur on the. surfaces of polymers treated by energetic particles. A typical process is the so-called hydrophobic recovery, during which hydrophilic surfaces created by surface treatments become hydrophobic with elapsed time after treatment [98, 114, 115]. 

Check the chemical changes occurring due to elapsed time-dependent surface dynamic phenomena by performing elapsed time-dependent surface analysis. Hydrophobic recovery, for instance, may sometimes be reduced by using solvent-extracted, oligomer-free polymers as a starting material (115). 

The same hyperbranched polyglycerol modified with hydrophobic palmitoyl groups was used for a noncovalent encapsulation of hydrophilic platinum Pincer [77]. In a double Michael addition of ethyl cyanoacetate with methyl vinyl ketone, these polymer supports indicated high conversion (81 to 59%) at room temperature in dichloromethane as a solvent. The activity was stiU lower compared with the noncomplexed Pt catalyst. Product catalyst separation was performed by dialysis allowing the recovery of 97% of catalytic material. This is therefore an illustrative example for the possible apphcation of such a polymer/catalyst system in continuous membrane reactors. 

The formation of two aqueous phases can be exploited in the recovery of proteins using liquid-liquid extraction techniques. Many factors contribute to the distribution of a protein between the two phases. Smaller solutes, such as amino acids, partition almost equally between the two phases, whereas larger proteins are more unevenly distributed. This effect becomes more pronounced as protein size increases. Increasing the polymer molecular weight in one phase decreases partitioning of the protein to that phase. The variation in surface properties between different proteins can be exploited to improve selectivity and yield. The use of more hydrophobic polymer systems, such as fatty acid esters of PEG added to the PEG phase, favors the distribution of more hydrophobic proteins to this phase. In Fig. 10.13, partition coefficients for several proteins in a dextran-PEG system are given [27]. 

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