Ions, ion‐pairs, and their agglomerates

Szwarc, M.

doi:10.1002/macp.1965.020890104

Cited by 27 publications

(4 citation statements)

References 59 publications

(4 reference statements)

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“…Chem. Soc., 87, 1853(1965. at ~20°,4•6 and similar studies support the interpretation that it can be a major radiolytic mechanism.7b The fates of the positive ions in liquid and solid alkyl iodides have not been determined, but recent work with -irradiated alkyl iodides in rigid matrices at -196°s hows fairly complicated optical absorption spectra.…”

Section: Repeatedmentioning

confidence: 79%

Reactivities of contact and solvent-separated ion pairs. Anionic polymerization of styrene in dimethoxyethane

Shimomura¹,

Smid²,

Szwarc³

1967

J. Am. Chem. Soc.

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Detailed studies of anionic polymerization of sodium and cesium salts of living polystyrene in dimethoxyethane (DME) led to the absolute rate constants of propagation for the -S-,Na+ and -S-,Cs+ ions pairs as well as for the free -S-ions. These constants were determined over a temperature range +SO to -60°, providing therefore the necessary data for the calculation of the respective activation energies. The Arrhenius plot of the propagation constant of the -S-,Na+ ion pair produced a curve with a maximum at 0". This behavior was fully rationalized by assuming the presence of contact and solvent-separated -S-,Na+ ion pairs. An analysis of the data led to the absolute rate constant of the solvent-separated ion pair. The thermodynamics of the dissociation and solvation processes involving ion pairs was fully elaborated.etailed studies of the kinetics of anionic polym-D erization revealed that its propagation involves ion pairs and free Living polymer systems offer many advantages in such investigations. Apart from an increase in the chain length, which does not affect its rate of growth, the initial and final states of the propagating species remain the same.-S-,Na-+ S --S-,Na+ i.e., the sodium salt of an n-meric living polystyrene (-S-,Na+) is converted on the addition of a styrene molecule (S) into an ( n + 1)-meric specie. Therefore, the progress of the reaction does not disturb the equilibrium established between the ion pairs and free ions or between the different types of ion pairs.

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Section: Repeatedmentioning

confidence: 79%

Reactivities of contact and solvent-separated ion pairs. Anionic polymerization of styrene in dimethoxyethane

Shimomura¹,

Smid²,

Szwarc³

1967

J. Am. Chem. Soc.

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“…It is known that the non‐polar solvents presumably favored contact ion pair formation, which usually resulted in the formation of polymers with less syndiotacticity. In contrast, polar solvents such as dihloromethane and chloroform allow the formation of the less sterically crowded syndiotactic units, presumably because of sufficient ion pair separation 31, 69, 70. Thus, the formation of syndiotactic polymers in cationic polymerization reactions of α‐methylstyrene involves greater free ion character in the active end group, as explained on the basis of mechanistic considerations and kinetic effects 27.…”

Section: Resultsmentioning

confidence: 99%

Partitioned partial least squares regression with application to a batch fermentation process

Andersen

Runger

2011

Journal of Chemometrics

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The performance of Partial Least Squares regression (PLS) in predicting the output with multivariate cross-and autocorrelated data is studied. With many correlated predictors of varying importance PLS does not always predict well and we propose a modified algorithm, Partitioned Partial Least Squares (PPLS). In PPLS the predictors are partitioned into smaller subgroups and the important subgroups with high prediction power are identified. Finally, regular PLS analysis using only those subgroups is performed. The proposed Partitioned PLS (PPLS) algorithm is used in the analysis of data from a real pharmaceutical batch fermentation process for which the process variables follow certain profiles during a specific fermentation period. We observed that PPLS leads to a more accurate prediction of the yield of the fermentation process and an easier interpretation, since fewer predictors are used in the final PLS prediction. In the application important issues such as alignment of the profiles from one batch to another and standardization of the predictors are also addressed. For instance, in PPLS noise magnification due to standardization does not seem to create problems as it might in regular PLS. Finally, PPLS is compared to several recently proposed functional PLS and PCR methods and a genetic algorithm for variable selection. More specifically for a couple of publicly available data sets with near infrared spectra it is shown that overall PPLS has lower cross-validated error than PLS, PCR and the functional modifications hereof, and is similar in performance to a more complex genetic algorithm.

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“…They are killed by water, oxygen and a high number of electrophilic substances. Operating in absence of killing impurities one obtains stable living species; they are ionic species whose exact form (free ion, contact ion-pair, solvent separated ion-pair [14][15][16][17] depends upon the concentration and the nature of the monomer, the counterion and the solvent; polar Preparation and Study of Block Copolymers with Ordered Structures 89 solvents favor the dissociation of ion-pairs while non polar mediums favor their association. The different species present during the polymerization participate in the growing chains according to their reactivity and some species can even have an influence on the stereo-regularity of the polymers formed.…”

Section: ) Propagationmentioning

confidence: 99%

Preparation and study of block copolymers with ordered structures

Gallot

Structure and Properties of Polymers

109

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Ions, ion‐pairs, and their agglomerates

Cited by 27 publications

References 59 publications

Reactivities of contact and solvent-separated ion pairs. Anionic polymerization of styrene in dimethoxyethane

Reactivities of contact and solvent-separated ion pairs. Anionic polymerization of styrene in dimethoxyethane

Partitioned partial least squares regression with application to a batch fermentation process

Preparation and study of block copolymers with ordered structures

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