Poly transformation extent

It was found that in spite of the large excess of modifying amine (N-isopropyl-, -diethyl, -dipropyl, -diisopropyl, -n-hexyl, -cyclohexyl, -n-octyl), the extent of substitution did not exceed 5-10 molar %. For the case of the N-isopropyl derivative, i.e. [poly(AAm-co-NiPAAm)], the authors connected such results with the temperature-induced conformational transformation of partially hydrophobized copolymer acquiring the contracted conformation, "... which made it difficult for N-isopropylamine to react further with the amide groups [22], Unfortunately, no data on the solution behaviour of these interesting copolymers have been reported to date, although there is a high probability that they would demonstrate certain properties of the protein-like macromolecules. At least, in favour of similar supposition is supported by the results of our studies [23] of somewhat different PAAm partially hydrophobized derivative, whose preparation method is depicted in Scheme 3. 

Bioactive macromolecules like peptides, proteins, and nucleic acids have been successfully embedded in planar LbL films. An important question is the retention of the bioactivity of the film-embedded biomolecules. The structural properties and stability of the LbL films formed from synthesized polypeptides of various amino acid sequences were recently reported [50]. The authors showed that control over the amino acid sequence enables control over non-covalent interpolypeptide interaction in the film, which determines the film properties. Haynie and coworkers showed by circular dichroism spectroscopy that the extent of adsorption of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) in the LbL films scales with the extent of secondary structure of the polypeptides in solution [51]. Boulmedais demonstrated that the secondary structure of the film composed of these polypeptides is the same as the peptide structure in the complex formed in solution [52], as found by Fourier transform IR spectroscopy (FUR). 

In order to follow the fate of SnCl4 during the initiation of formaldehyde polymerization at —78°C in toluene, the polymer suspension was filtered at low conversion. After 2 min reaction time, no tin could be detected in the filtrate, all the tin being adsorbed on the polymer. The same result was obtained in BF3. etherate initiated formaldehyde polymerization in toluene all the boron was adsorbed by the polymer. This result could mean that initiation is almost instanttmeous and all the initiator was used for initiation. Alternatively, the initiator could have been partially used for initiation but the rest of the initiator was quantitatively adsorbed by the polymer formed. Adsorption experiments showed that SnCl4 at —78° in toluene is only adsorbed to an extent of 25% after 120 min on high surface area poly formaldehyde. These experiments still do not exclude the possibility that a substantial portion of all SnCl4 in toluene is coordinated to the initially formed polymer and only a small portion is transformed into the actual initiator. 

On the other hand, the other direction of addition (yd-addition) produces a monosubstituted alkylidene that is sterically comparable to the initiating alkylidene, making this the desired direction of addition. Formation of a six-membered ring in a reaction involving a more reactive terminal alkylidene would transform 43b into 44b. The NMR spectrum of poly-6 reveals two carbonyl carbon resonances. Therefore it was speculated that poly-6 consist of a random distribution of five- and six-membered rings formed through what is nominally tail-to-tail and head-to-head cyclopolymerization of the two acetylenic bonds in the same monomer (Scheme 1). Other uncertainties in catalyst systems of the type are the rate at which alkylidene rotamers interconvert, the extent to which the reactivities of the two alkylidene rotamers differ, and the degree of selective formation of one rotamer when a triple bond reacts with a Mo=C bond. ... 

Fig. 10.3 Plot of the extent of transformation, (1 - k), against log time for the crystallization of hydrogenated poly(butadienes) at the indicated temperatures. The weight-average molecular weights and mol percent branch points are indicated.(3)...

M = 2 X 10" to 2 X 10 , from dilute solutions of either /7-xylene or ethanol showed good adherence to the derived Avrami equation with n = 4, over an appreciable extent of the transformation.(33,34) An unfractionated isotactic poly(propylene), 3.6 X 10 , yields a set of superposable isotherms, when crystallized from a 0.3% solution of either ether tetrahn or decaUn.(35) A plot of the data according to Eq. (9.32) that is given in Fig. 13.14 makes clear both the superposition and adherence to a derived Avrami expression. In this case the exponent n is again found to be 4. An exponent of 4 has also been found for poly(ethylene terephthalate) crystallizing from several different solvents.(36)... 

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