Effects of cross-linkers

The effect of the ionic strength of the solution on the hydrolysis rate of the gel has been studied. Rapid hydrolysis of the gel was observed with a decrease in ionic strength of the solution, i.e., a higher degree of swelling with a lower ionic strength of the solution [128]. It was concluded that the hydrolysis of the gel could be controlled by the amount of the cross-linker added. In their further studies, the effect of cross-linker on the swelling behavior of the gel has been studied [128]. 

Figure 31.8 Effects of cross-linker concentration CU3 on the ionic conductivity and Tg of the IL-type network polymer PfceTFSI-CLfg).

Effect of Cross-linker Reactivity on Experimental Gel Points... 

Figure 3. Effect of cross-linker level on cure characteristics. (Monsanto rheometer curves - 307...

Clarke SM, Hotta A, Tajbakhsh AR, Terentjev EM, 2001. Effect of cross linker geometry on equilibrium thermal and mechanical properties of nematic elastomers. Phys Rev E 64 061702. 

Gao, H. Miasnikova, A. Matyjaszewski, K. Effect of cross-linker reactivity on experimental gel points during ATRP of monomer and cross-linker. Macromolecules 2008, 41 (21), 7843-7849. 

H.-Y. Zhao, Y.-M. Cao, X.-L. Ding, M.-Q. Zhou, Q. Yuan, Effects of cross-linkers with different molecular weights in cross-linked Matrimid 5218 and test temperature on gas transport properties, J. Membr. Sci., 323, 176-184 (2008). 

The effect of cross-linker concentration in the range of 1.0-10.0 mM was checked by XPS no obvious differences were observed with a molar ratio of 2 cross-linkers to 1 primary amine. Thus, a 5.0 mM solution was used as the standard. All the experiments were carried out at 20 C under an ambient atmosphere. The main variable is the reaction time, which is an important parameter, controlling both the extent of reaction and the surface uniformity. Figure 5 shows the relationship of the atomic ratio N/Si (XPS) with the incubation time. The reaction is very fast within the first 10 min, reaching its maximum after approximately 30 min. 

Deficiency of cross-linker molecules (off-balancing of stoichoimetry) was found to increase the relaxation exponent value [7, 65, 66]. The gel becomes more lossy , and stress relaxation is accelerated. Adding of a non-reacting low molecular weight solvent also increases the relaxation exponent [58, 65], even in physical gels [67]. Both effects have been attributed to screening [44, 65],... 

To maximize the modification of amines and minimize the effects of hydrolysis, maintain a high concentration of protein or other target molecule in the reaction medium. By adjusting the molar ratio of cross-linker to the target molecule(s), the level of modification and conjugation may be controlled to create an optimal product. 

An alternative approach to effect chiral discrimination is to use the technique of molecular imprinting, the subject of this book. This technique, sometimes also referred to as template polymerisation, results in synthetic polymers of predetermined selectivity. Receptor-like binding sites are tailor-made in situ by the copolymerisation of cross-linkers and functional monomers, which are interacting with... 

To obtain a series of L-phenylalanine anilide (L-PheNHPh) MIPs with varying MAA L-PheNHPh ratios, Sellergren [64] kept the template and the total monomer concentrations constant and changed the amount of MAA and therefore the amount of cross-linker must also have changed. Using a chromatographic system to assess these polymers he found that maximum selectivity occurred at a different concentration of MAA to that of maximum capacity. However, it has already been observed that varying the amount of cross-linker affects the selectivity of the polymer and hence the observed effects are difficult to interpret. 

Conditions of polymerization like temperature ( 7°C or 40°C what means below or above the phase transition temperature in pure water), nature of solvent (water or water/ethanol 50/50 mixture to use hydrophilic or more hydrophobic photo initiators), amount of cross-linker and monomer concentration can be varied to investigate the effect of reaction conditions on the swelling behaviour, phase transition temperature and morphology. Photo patterning of hydrogels can be done in the presence of an adhesion promoter on glass substrate (Singh et al. 2006). 

Atom transfer radical polymerization (ATRP) was selected as an exemplary CRP technique to systematically study the kinetics and gelation behavior during the concurrent copolymerization of monovinyl monomers and divinyl cross-linkers (Scheme 2). The effect of different parameters on the experimental gelation was studied, including the initial molar ratio of cross-linker to initiator, the concentrations of reagents, the reactivity of vinyl groups present in the cross-linker, the efficiency of initiation, and the polydispersity of primary chains. Experimental gel points based on the conversions of monomer and/or cross-linker at the moment of gelation, were determined and compared with each other in order to understand the influence of each parameter on the experimental gel points. 

Achieving a suitable particle size with better yield is important in precipitation polymerization as many parameters affect its mechanism. We have prepared GA based MIPs by the precipitation polymerization and observed the effect of porogen on particle size and specific molecular recognition properties (Pardeshi et al, 2014], MIP, M-lOO prepared in the porogen acetonitrile and MIP, M-75 prepared in a mixture of acetonitrile-toluene (75 25 v/v), resulted in the formation of microspheres with approximately 4 pm particle size and surface area of 96.73 m g and nanoparticles (0.8-1000 nm] and a surface area of 345.9 m g" respectively. The results have shown that effect of toluene on the particle size of MIPs depends on the type of cross-linker used and its solubility parameter. Matching the solubility parameter of solvent mixture and cross-linkers is important to obtain the desired particle size in MIPs. The MIPs selectively recognized GA in presence of its structural analogues. Pure GA with percent recovery of 75 ( 1.6) and 83.4 ( 2.2) was obtained from the aqueous extract of herb Emblica officinalis by M-lOO and M-75, respectively. 

In the field of water purification technology by membrane filtration, many researchers have studied the effect of cross-linking agents on membrane performance by varying the cross-linking conditions. The desired permeation and selectivity properties of the top thin layer vary with the concentration of polymer and cross-linking conditions like temperature and concentration of the cross-linker. Miao et al. [24] prepared... 

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