Diisocyanate-PEO

This mechanism of initiation is confirmed by the fact that, when the PAN-PEO block copolymer is treated with diisocyanate in benzene in the presence of pyridine acting as catalyst, copolymers lose their solubility in DMF as a result of the formation of intermolecular chemical bonds75). 

Preparation of polyfethylene oxide) (PEO) and poly(arylene ether) based hydrophilic-hydrophobic block copolymer is of special interest because PEO has been proven to be particularly reliable and versatile for the surface modification of biomaterials. The first poly(ediylene oxide)-/ /oc/c-polysulfonc (PEO-fc-PSF) copolymers were reported by Aksenov et al.217 They employed diisocyanate chemistry to link hydroxy-terminated sulfone oligomers and polyfethylene... 

Parallel tests show that thrombin adsorption is minimal on well-prepared polyurethanes containing amorphous PEO, greater on PTMO, and very high on analogues of the hard segment (diisocyanate-diamine copolymers), thus paralleling the trends in platelet retention index p. This result is consistent with the postulate that protein adsorption must precede platelet adsorption. 

Key PEi 2, polyether sequence (from a,a)—dihydroxy precursor) PTMO, PPO, or PEO, HSDI, diisocyanate residue in hard-segment phase (TDI, MDI, or IPDI) CDI, connector diisocyanate residue (TDI only) and ED, ethylenediamine residue. 

PEO and PPO, are mixed to create Type III segmented polyurethanes, three different diblock sequences of equal probability must be obtained PEO-PEO, PEO-PPO, and PPO-PPO are the principal species. The same principles that govern the formation of l-,3-,5-,-7... unit combination of diisocyanates and diamines in the hard segment, also predict that the reaction product of 2 mol of a, co diol with 1 mol of diisocyanate after Step 1 of the three-step process (Figure 2) will consist mostly of the monomer (the diol), some of the desired trimer (diol -TDI-diol), but also some of the pentamer (diol-TDI-diol-TDI-diol), etc. 

An added complicating factor arises in what we will call Type III and Type IV polyurethanes. These are similar to Type I and Type II respectively, but instead of using a pure polyether in the first step a 1 1 mixture of PPO 1200 and PEO 1000 is used. In this case the sequences of ether chains connected by a diisocyanate residue or a "hard" segment can be PPO-PPO, PPO-PEO or PEO-PEO. 

Enzymes were incorporated into nanofibers viaelectrospinning, and subsequent crosslinking the enzymes incorporated effectively prevented their leaching. In the presence of PEO or PVA, casein and lipase were electros-pun into ultra-thin fibers. After crosslinking with 4,4 -methylenebis(phenyl diisocyanate) (MDI), the fibers became insoluble, and the lipase encapsulated exhibited 6 times higher hydrolysis activity towards olive oil than that of the films cast from the same solution. The cross-linked enzymes in nanofibers showed very high activity and stability. For example, the immobilized a-chymotrypsin in a shaken buffer solution maintained the same activity for more than two weeks. 

Recently Chelmecki et aL reported the ionic conductivity results of HPC-PEO networks containing LiN(CF3S02)2- These networks were obtained by thermal crosslinking of HPC with tri(ethylene glycol) and toluene diisocyanate through the urethane bonds, as shown in Fig. 3.1. The ionic conductivities of these samples were in the range of 10 S/cm. The... 

Low temperature (183 K) Li NMR spectrum of the polymer electrolyte formed by hydroxyl ethyl cellulose (HEC) grafted with PEO-diisocyanate (DPEO) complexed with lithium perchlorate (a) Li NMR spectra (b) Li-( H decoupled spectra. 

---