End hydroxyl

Further work related to the synthesis of copolymers with either P2VP or P4VP blocks has been reported in the literature. Triblock terpolymers PS-fc-P2VP-fo-PEO were synthesized in THF at - 78 °C by sequential polymerization of styrene and 2VP, initiated by s-BuLi in the presence of IiCl [25]. The living polymer was terminated with EO. The end-hydroxyl group was... 

Both reactions lead to the appearance of end hydroxyl and unsaturated groups in the polymer. The accumulation rate of these groups is expected to be controlled by the concentration of the active propagating sites (see Fig. 13) in accordance with Scheme (43). 

After the elastomer is washed with water, the macromolecule obtains end hydroxyl groups ... 

With a proper choice of mobile phase (aqueous or nonaqueous), many commercially columns are available for SEC of PVP and VP-based copolymers. Mobile-phase modifiers (such as methanol, salt, and buffer) are normally required to eliminate interactions with columns. A single linear or mixed-bed column has been found to provide good separation of PVP and VP-based copolymers with a molecular weight range of from a few thousands to several millions. In general, the aqueous SEC system has better long-term stability and provides better separation than the nonaqueous SEC system, especially at the low-molecular-weight end. Hydroxylated methyl-methacrylate-type columns and water-methanol mobile phase (50 ... 

The polyfunctional initiator method provides the possibility to prepare end-functionalized stars by deactivating the living branches by suitable electrophilic terminating agents. Polystyrene (PS) and PEO stars having end hydroxyl groups were prepared by this method.1519... 

Problem 5.4 In another series of experiments similar to those in Problem 5.1 the low-molecular weight polyester corresponding to 82% conversion of the original COOH groups were further polymerized at 161°C in the presence of p-toluene sulfonic acid (0.004 mol per mol of polymer) yielding the following conversion data [5] of the end hydroxyl and carboxyl acid groups ... 

In115 116) the cationic polymerization of cyclic ethers was examined theoretically and experimentally with regard to the nature of MWD variation. A theoretical analysis was made of how MWD is affected by the depolymerization reactions, monomole-cular deactivation of active centers, recombination of active centers, chain transfer by hydroxyl-containing compounds, chain transfer to the monomer, and ether oxygen of the polymer chain, as well as via the end hydroxyl group. 

Oxygen forms many compounds with chlorine and with chlorine end hydroxyl but none of them can be produced by direct combination, llie following list contains all that are known s—... 

The first step is the attack of a nucleophile on an epoxide. It s an Sn2 reaction, because it goes with inversion of configuration, and we need a phenol as the nucleophile. To make the phenol more reactive, we probably want to deprotonate it to make the phenoxide, and NaOH will do this. Why does this end of the epoxide react Well, it is next to a phenyl ring, and benzylic Sn2 reactions are faster than reactions at normal secondary carbons. Next the end hydroxyl group is made into a leaving group (a mesylate ), for which we need methanesulfonyl chloride (mesyl chloride) and triethylamine. The primary hydroxyl group must react faster than the secondary one because it is less hindered. 

MP PDEG in the composition of the polyester resin has end hydroxyl and carboxyl groups capable of interacting with the isocyanate groups. To prevent the chemical interaction of the individual IPN networks, the MP PDEG end groups were pre-blocked with a monofunctional isocyanate (phenyl isocyanate) later this reaction was excluded with almost no effect upon the adhesive properties. 

Cohen-Addad, J. P. Ebengou, R., Silica-Siloxane Mixtures. Investigations into Adsorption Properties of End-Methylated and End-Hydroxylated Chains. Polymer 1992, 33,379-383. 

On the other hand, azophenol 04-podand 6 n = ) shows the complexation-coloration with prim, and sec. amines, included sterically bulky amines such as /-BUNH2, (/-Pr)2NH, and 2,2,6,6-tetramethylpiperidine. Consequently, the combined use of two types of azophenol hosts, 2 and 6, is highly useful to discriminate the substitution pattern of amines by means of coloration. The two end hydroxyl groups in the dyed podands are required for such discrimination of the amine pattern because no complexation-coloration is observed by addition of various amines when the hydroxyl groups are substituted with methoxyl groups. 

Fig. 12.Samples of polyfenylenesulfones (polymerization degree n = 1-6) separated under critical conditions. Symbols without hydroxyl groups (f=0), one end hydroxyl group (f=l). A comparison with the SEC chromatogram illustrates that LCCC separates the samples independently of the size of macromolecules (From [130] with permission)...

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