Crosslinking experimental procedures

The study of acid-base interaction is an important branch of interfacial science. These interactions are widely exploited in several practical applications such as adhesion and adsorption processes. Most of the current studies in this area are based on calorimetric studies or wetting measurements or peel test measurements. While these studies have been instrumental in the understanding of these interfacial interactions, to a certain extent the interpretation of the results of these studies has been largely empirical. The recent advances in the theory and experiments of contact mechanics could be potentially employed to better understand and measure the molecular level acid-base interactions. One of the following two experimental procedures could be utilized (1) Polymers with different levels of acidic and basic chemical constitution can be coated on to elastomeric caps, as described in Section 4.2.1, and the adhesion between these layers can be measured using the JKR technique and Eqs. 11 or 30 as appropriate. For example, poly(p-amino styrene) and poly(p-hydroxy carbonyl styrene) can be coated on to PDMS-ox, and be used as acidic and basic surfaces, respectively, to study the acid-base interactions. (2) Another approach is to graft acidic or basic macromers onto a weakly crosslinked polyisoprene or polybutadiene elastomeric networks, and use these elastomeric networks in the JKR studies as described in Section 4.2.1. 

Fig. 12 demonstrates that the novel technique allows direct reaction of the biomolecules with the silyl modified, aldehyde-functionalized surface to form Schiff base linkages between CHO and NH2 groups (route B), thus eliminating the use of a crosslinking agent like GA. Omitting details of the experimental procedures [11] the results of three different immobilization methods are displayed in Fig. 13 presenting a comparison with the physisorptive attachment of GOD on native, underivatized CPG. 

During emulsion polymoization proccesses crosslinking can occur due to the presence of radicals and unsaturation in the polymer chain. Chain transfer agents are often used to decrease the level of crosslinking during polymerization. The gel content of a crosslinkable polymo is d ned as the fraction of material of infinite MM experimental criteria are usually more aibitraiy, and strongly depend on the experimental procedure. The same holds for the gel point, Le. the conversion at which the first insoluble polymer network makes its appearance. For example, in ABS gel content can be based on the toluene extraction of the soluble fraction of the polybutadioie. Hie insoluble residue is the gel fraction by definition. 

The crosslink density of the hydrogels was calculated using Flory-Rehner equation. The experimental procedure involved weighing of PAAM before immersing into water. The swollen samples were taken out and dried at room temperature after equilibrium was reached. Final weight of the swollen sample was recorded and compared to that of the original weight. The Flory-Rehner equation [19] is explained as ... 

The core-shell particles were prepared by seeded semi-continuous emulsion polymerization under monomer-starved conditions. A detailed experimental procedure for similar latices is given by Winnik et al. [20] and Kruger et al. [21]. The seed was prepared by batch emulsion polymerization. After synthesizing the PBMA core a highly crosslinked PnBA-shell with MAA comonomer... 

For the same polymer and curing procedure, networks formed in the presence of various diluents (

Kinetic theory requires C

volume fraction of polymer during solution cure), assuming comparable numbers of crosslinks per primary molecule are introduced. Experimentally C,

state cures, although they do decrease somewhat in the more dilute curing systems (q> < 0.2). Solution cured polydimethyl siloxane networks show similar behavior in their dry state moduli (275). 

In the following, a detailed description of the two-step crosslinking procedure, including many practical details that proved to be useful in order to obtain high quality samples will be presented. Readers not interested in experimental details can proceed below. 

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