Viscosity – Molecular Weight Relationships and Unperturbed Dimensions of Linear Chain Molecules

Poly(alkyl itaconates): 4. Glass and sub-glass transitions in the di-alkyl ester series, methyl to hexyl

The sterically hindered monomers dibutyl itaconate (DBI) and dicyclohexyl itaconate (DCHI) were polymerized via reversible addition fragmentation chain transfer (RAFT) free-radical polymerization. S,S'-Bis(alpha,alpha'-dimethyl-alpha"-acetic acid) trithiocarbonate, cumyl dithiobenzoate, and cumyl phenyldithioacetate have been used as RAFT agents to mediate a series of polymerizations at 65 degreesC yielding rod polymers ranging in number average molecular weight from 9000 to 92,000 g mol(-1). The progress of the polymerization was followed via online Fourier transform-near infrared spectroscopy. The polydispersity indices of the obtained rod polymers were relatively high at 1.4-1.7. The RAFT polymerizations of the hindered monomers used in the present study displayed both ideal living and hybrid behavior between conventional and living polymerization, depending on the RAFT agent used. DCHI rod polymers generated via the RAFT process were subsequently reinitiated in the presence of styrene to produce a range of BAAB and A-B rod-coil block copolymers of molecular weights up to 164,000 g mol(-1). The chain extension yields molecular weight distributions that progressively shift to higher molecular weights and are unimodal. Thermogravimetric analysis of the pDCHI-block-pStyrene copolymers indicates thermal degradation in two separate steps for the pDCHI and pStyrene blocks. (C) 2004 Wiley Periodicals, Inc.

Reversible addition fragmentation chain transfer polymerization of sterically hindered monomers: Toward well-defined rod/coil architectures

Electrospray ionization-quadrupole ion trap mass spectrometry (ESI-MS) was utilized to access the polymeric product spectrum generated by the pulsed laser polymerization (PLP) of methyl acrylate (MA) at -35 degrees C in the presence of the photoinitiators 2,2-dimethoxy-2-phenylacetophenone (DMPA), benzoin, benzoin ethyl ether (BEE), and bis(2,4,6-trimethylbenzoyl)phenylphosphinoxide (Irgacure 819) to study the reactivity of primary and potential secondary derived radical fragments from photolytically induced fragmentation. Similarly, the polymeric products generated from the PLP of dimethyl itaconate (DMI) at 0 degrees C using the aforementioned photoinitiators as well as benzil and 2,2'-azobis(isobutyronitrile) (AIBN) were studied using ESI-MS. The PLP products of methyl methacrylate (MMA) initiated with Irgacure 819 at -25 degrees C were also examined. Polymerization systems utilizing Irgacure 819 give complex product spectra due to the formation of second generation radical species resulting in several initiator fragments incorporated into a single polymer chain. Termination products, both combination and disproportionation, were identified with high accuracy. The reactivity of the various derived radical fragments toward the monomers employed is summarized for the current and a previous study in tabular form. Energy deposition into the MA/photoinitiator systems is found to have no influence on the product distributions of the MA polymers produced via photoinitiation under the conditions examined. For various photoinitiators employed, products congruent to that of chain transfer to monomer species in the DMI photopolymerizations are observed, conclusively illustrating that chain transfer to monomer is a significant reaction pathway in itaconate free radical polymerizations.

Mapping photolysis product radical reactivities via soft ionization mass spectrometry in acrylate, methacrylate, and itaconate systems

Apparent molecular weights from size exclusion chromatography, that is molecular weights relative to standards of a nature different to that of the polymer sample being studied, are frequently used. We use calculations corresponding to realistic cases to provide guidelines for situations when, and to what extent, apparent molecular weights (MWs) can be meaningful. In controlled polymerization, we show how, without due care, use of apparent MW, could lead to the incorrect conclusion that the reaction was not controlled, whereas the true MWs would be close to theoretical values. We show here that the quality of the eluent as a solvent for the standard and the polymer sample is a good indication of the accuracy and the significance of the apparent polydispersity index. Accurate Mark-Houwink-Sakurada parameters are of limited availability, but the data about solvent quality available in handbooks or available from static light scattering measurements. Apparent Mn is of no use in controlled polymerization if simple simulations as performed in this work do not validate their use. The determination of transfer constants by the Mayo plot can be performed using apparent Mn without introducing any significant error, contrary to apparent weight-average molecular weight Mw or apparent ln number distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 897-911, 2008

Using apparent molecular weight from SEC in controlled/living polymerization and kinetics of polymerization

KUHN-MARK-HOUWINK-SAKURADA relations for poly(dimethyl-, diethyl-, di-n-propyl-, di-n-butyl-, di-n-hexyl-, di-n-octyl-, di-n-decyl-, and di-n-undecyl itaconate) were established in toluene at 25°C. The decreasing exponent a from 0.80 to 0.61, in going from lower to higher members of the series, reflects the decreasing solvent power of toluene. Observed high molecular weights of the polymers are in disagreement with formerly assumed strong chain transfer to monomer in the propagation step. σ-parameters, evaluated according to the KURATA-STOCKMAYER extrapolation procedure, within limits of 1.98 and 3.50, indicate strong and progressively increasing steric hindrance to free rotation in this polymer homologueous series.



KUHN-MARK-HOUWINK-SAKURADA-Gleichungen wurden fur Poly-(dimethyl-, diathyl-, di-n-propyl-, di-n-butyl-, di-n-hexyl-, di-n-octyl-, di-n-decyl- und di-n-undecylitaconat) in Toluol bei 25°C bestimmt. Die von den niederen zu den hoheren Gliedern der Polymerenreihe von 0,80 bis 0,61 abnehmenden Werte des Exponenten a geben das abnehmende Losungsvermogen von Toluol wieder. Die beobachteten hohen Molekulargewichte der Polymeren stehen im Widerspruch zu der fruher vermuteten starken Kettenubertragung durch das Monomere bei der radikalischen Polymerisation. Die Grose der nach der KURATA-STOCKMAYERschen Extrapolationsmethode bestimmten σ-Parameter im Bereich von 1,98 bis 3,50 steht im Zusammenhang mit der stark zunehmenden sterischen Hinderung der freien Drehbarkeit fur diese polymerhomologe Reihe.

Slavica Vasović

Papers

KUHN‐MARK‐HOUWINK‐SAKURADA relations and unperturbed dimensions of poly(di‐n‐alkyl itaconates)