Olefin copolymerization via reversible addition-fragmentation chain transfer

Successful statistical copolymn. of an a-olefin (1-octene) with an acrylate (Bu acrylate, BA) and with a methacrylate (Me methacrylate, MMA), employing reversible addn.-fragmentation chain transfer (RAFT) mediated polymn. has been accomplishe

Chemical composition and topology of poly(lactide-co-glycolide) revealed by pushing MALDI-TOF MS to its limit

Software developed in house in combination with a recently developed method of MALDI-TOF MS enable not only the elucidation of individual chain structures of poly(lactide-co-glycolide), a polymer used extensively in the medical sector, but a full characterization of this copolymer including even its chemical composition and topology (random, gradient, block (see figure), or alternating)

Copolymer fingerprints of polystyrene-block-polyisoprene by MALDI-ToF-MS

MALDI-ToF-MS mass spectra of copolymers contain a lot of information on both chain length distribution (CLD) and chemical composition distribution (CCD). In this paper an approach for extracting detailed information from a MALDI-ToF-MS mass spectrum is presented that enables the study of microstructure for copolymers. More specifically, this paper is dealing with a polystyrene-block-polyisoprene copolymer, in which the growth of the second block is followed with MALDI-ToF-MS as a function of conversion. The technique is compared to 1H NMR for the evaluation of average chemical compositions, revealing that ionization efficiencies do not influence the obtained mass spectra. It is shown that MALDI-ToF-MS can extract detailed information on the chain length distributions (CLDs) for both polystyrene and polyisoprene blocks. Using random coupling statistics, it is shown that the proposed analysis yields results with a high accuracy

Application of matrix-assisted laser desorption ionization time-of-flight mass spectrometry in pulsed laser polymerization : chain-length-dependent propagation rate coefficients at high molecular weight : an artifact caused by band broadening in size exclusion chromatography?

The combination of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF-MS) and size exclusion chromatog. (SEC) combined with pulsed laser polymn. has been used to evaluate propagation rate coeffs. (kp) in bulk free-radical polymn. for the systems Me methacrylate and styrene. By varying laser frequencies, the relation between polymer chain length and obsd. propagation rate coeff. (kpobs) has been investigated in detail. It has been found that deviations between MALDI-ToF-MS and SEC at higher mol. wts. are the result of instrumental effects in SEC. Moreover, using a model and taking into account exptl. studies on the propagation of oligomeric species, it has been inferred that the relationship between kpobs and polymer chain length is the result of chain-length-dependent behavior of the true kp in the oligomeric range, therewith excluding any chain-length-dependent behavior at higher mol. wts

Method to isolate and characterize oligomers present in the aqueous phase in emulsion copolymerization

In order to model the entry of radical in emulsion copolymerization, a study of the oligomers present in the aqueous phase is necessary. In this work a new method for separation and characterization of the aqueous phase has been developed. MALDI-ToF-MS was found to be a powerful technique in order to characterize the oligomers present in the aqueous phase. It is for the first time that full chemical composition and molecular weight information of the oligomers present in the aqueous phase in emulsion copolymerization has been obtained. The methodology was shown to be semi-quantitative and several factors were studied, for example temperature effects, interference of latex particles present in serum of the aqueous phase and type of ionizing salt in MALDI. It was shown that the methodology works well, even though we are dealing with small quantities of oligomers and the possibility of mass discrimination in MALDI-ToF-M

Ester-functionalized polycarbonates obtained by copolymerization of ester-substituted oxiranes and carbon dioxide: A MALDI-ToF-MS analysis study

Two ester-functionalized cyclohexene oxide monomers (3,4-cyclohexene-oxide-1-carboxylic acid methyl ester (1) and 3,4-cyclohexene-oxide-1-carboxylic acid phenyl ester (2)) could be copolymerized with CO2 using the ß-diketiminato zinc catalyst (EtBDI)ZnOEt (EtBDI = 2-(2,6-diethylphenyl)amido-4-(2,6-diethylphenyl)imino-2-pentene) under mild conditions. MALDI-ToF-MS microstructure analyses of the formed aliphatic polycarbonates revealed the occurrence of chain transfer reactions to both monomer and polymer as a result of zinc-catalyzed transesterifications. As a consequence, branched and cyclic polymer structures were formed, which limited the molecular weight development and led to an increase in the polydispersity. The zinc catalyst is also capable of transesterifying carbonate functionalities, albeit that the transesterification rate is considerably lower than that for ester functionalities and only becomes visible at high conversion. This was supported by independent catalytic transesterification reactions of esters and carbonates. Transesterification of carbonate functionalities at the end of the polymerization reaction might explain the observed bimodal behavior for the intrinsically living ß-diketiminato zinc catalyst