Of cross-linked polymers

Methylquinohnes react with chloromethylphenyl groups of cross-linked polymers to form anion-exchange resins (86). 

Elastomers are a special sort of cross-linked polymer. First, they are really linear polymers with just a few cross-links - one every hundred or more monomer units - so that a molecule with a DP of 500 might have fewer than five cross-link points along its length. And second, the polymer has a glass temperature which is well below room temperature, so that (at room temperature) the secondary bonds have melted. Why these two features give an elastomer is explained later (Chapter 23). 

FIGURE 19.4 Elution of cross-linked polymer from 5- and 20-/u.m particle size columns. 

HOPC uses solid porous materials such as porous silica. Most of the porous gels made of cross-linked polymers, widely used in SEC, will not be appropriate. It is necessary to use porous materials that withstand a high... 

Other applications are based on the use of solutions of reversed micelles as templates. For example, solutions of reversed micelles have been employed as a matrix to control the porosity of cross-linked polymer resins. The pore size of the polymers was controlled by varying the amounts of water in the AOT-reversed micelles [67]. 

Dusek, K, Diffusion Control in the Kinetics of Cross-Linking, Polymer Gels and Networks 4, 383, 1996. 

Fig. 9.6 Photograph of cross-linked polymer stick in different states of swelling for the potential use as alignment medium. From left to right unswollen polymer stick in a standard 5-mm NMR tube, the unswollen polymer stick after polymerization, the polymer stick swollen in chloroform, and the...

PJ Flory, R Rehner Jr. Statistical mechanics of cross-linked polymer networks. J ChemPhys 11 521-525, 1943. 

OPPERMANN and rehage Structure of Cross-linked Polymers... 

The properties of a polymer network depend not only on the molar masses, functionalities, chain structures, and proportions of reactants used to prepare the network but also on the conditions (concentration and temperature) of preparation. In the Gaussian sense, the perfect network can never be obtained in practice, but, through random or condensation polymerisations(T) of polyfunctional monomers and prepolymers, networks with imperfections which are to some extent quantifiable can be prepared, and the importance of such imperfections on network properties can be ascertained. In this context, the use of well-characterised random polymerisations for network preparation may be contrasted with the more traditional method of cross-linking polymer chains. With the latter, uncertainties can exist with regard to the... 

The temperature dependence of the compliance and the stress relaxation modulus of crystalline polymers well above Tf is greater than that of cross-linked polymers, but in the glass-to-rubber transition region the temperature dependence is less than for an amorphous polymer. A factor in this large temperature dependence at T >> TK is the decrease in the degree of Crystallinity with temperature. Other factors arc the reciystallization of strained crystallites ipto unstrained ones and the rotation of crystallites to relieve the applied stress (38). All of these effects occur more rapidly as the temperature is raised. 

The photochemical reactivity of 1,2,3-thiadiazoles has been utilized in the formation of cross-linked polymers <1996CHEC-II(4)289>. No new developments in this area have been reported since the publication of CHEC-II(1996). 

The percent reaction was typically determined by elemental analysis however, in the case of cross-linked polymers, the percent reaction was also evaluated by titrating the amount of chloride liberated and by measuring the weight gain of the polymer resin. All three methods gave comparable results (within 2-3%). 

Scheme 8.1 Synthesis of cross-linked polymer beads via ring-opening metathesis precipitation polymerization. [Mo] = Mo(N-2,6-i-Pr2-...

---