Synthesis and Characterization of Copoly(Ether Sulfone)s with Different Percentages of Diphenolic Acid Units.

New functionalized Poly(ether sulfone)s having different molar ratio (10, 20, 30, 50, 70, 100 mol%) of 4,4-bis phenoxy pentanoic acid unit (diphenolic acid; DPA) units were synthesized and characterized by (1H and 13C)-NMR, MALDI-TOF MS, FT-IR, DSC and DMA analyses. The microstructural analysis of the copolymers, obtained by 13C-NMR using an appropriate statistical model, shows a random distribution of copolymer sequences, as expected. The presence of different amount of DPA units along the polymer chains affects the chemical and physical properties of the copolymers. The Tg and the contact angle values decrease as the molar fraction of DPA units increases, whereas the hydrophilicity increases. NMR and MALDI-TOF MS analyses show that all polymer chains are almost terminated with hydroxyl and chlorine as end groups. The presence of cyclic oligomers was also observed by MALDI-TOF MS analysis.

Analysis of melt copolymers.

Melt copolymer chains are the main (most abundant) reaction product obtained when heating a blend of two (or more) condensation polymers (such as polyester + polycarbonate or polyester + polyamide or polyester + polyester) in which exchange reactions occur. In fact, during the melt-mixing reaction, an AB copolymer is formed and, as a consequence, the sample is a complex mixture made of three components or simply "parts", referred to as Z1, Z2 and Z3, where Z1 and Z2 are the parts for unreacted homopolymers (A and B), whereas Z3 is the part for the copolymer. In this paper, it is shown that matrix-assisted laser desorption/ionization mass spectrometry (and mass spectrometry in general) can be used to monitor the yield of the reactive blending reaction, YR, by measuring the amount of unreacted homopolymer (Z1 and Z2). In order to allow for comparisons, the paper also discusses conventional methods for measuring Z1 and Z2, such as liquid chromatography and nuclear magnetic resonance.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with size-exclusion chromatographic fractionation for structural characterization of synthetic aliphatic copolyesters.

We report matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and off-line coupling of size-exclusion chromatography with MALDI-TOFMS analysis (SEC/MALDI-TOFMS) methods for the detailed characterization of poly[(R,S)-3-hydroxybutyrate-co-L-lactic acid], P[(R,S)-3HB-co-LA], and poly[(R,S)-3-hydroxybutyrate-co-epsilon-caprolactone], P[(R,S)-3HB-co-CL], copolymer samples which are expected to be used in special medical application as scaffolds for cartilage and soft tissue engineering. The novel copolyesters contained randomly distributed (R,S)-3-hydroxybutyrate structural units, were synthesized by transesterification of the corresponding homopolymers, i.e. atactic poly[(R,S)-3-hydroxybutyrate], a-PHB, and poly(L-Lactide) (PLLA) or poly(epsilon-caprolactone) (PCL), respectively. The MS methods used for the characterization of the resulting polydisperse copolyester samples were supported by classical methods (NMR, SEC). The structures of individual copolyester macromolecules, including end-group chemical structures, were established using initially MALDI-TOFMS and then SEC/MALDI-TOFMS. The compositions of the copolyesters were determined by two methods, namely based on 1H NMR and MALDI-TOF spectra. The two sets of values showed good agreement. The sequence distribution was determined using the signal intensities of individual copolyester macromolecules, which appeared in MALDI-TOF mass spectra. Furthermore, sequence analysis gave information about the degree of transesterification. The copolyesters synthesized, with only one exception, were demonstrated to be almost random, which implies that the ester-ester exchange was close to completion.

Molecular architecture of poly[(R,S)-3-hydroxybutyrate-co-6-hydroxyhexanoate] and poly[(R,S)-3-hydroxybutyrate-co-(R,S)-2-hydroxyhexanoate] oligomers investigated by electrospray ionization ion-trap multistage mass spectrometry.

A series of aliphatic copolyesters was obtained from (R,S)-beta-butyrolactone and two isomeric hydroxy acids, 6-hydroxyhexanoic and (R,S)-2-hydroxyhexanoic acids. The reactions were conducted in bulk without catalyst. Electrospray ionization tandem mass spectrometry (ESI-MSn) was used for molecular characterization of these copolyester oligomers. The mass spectra of the copolyesters studied have enabled identification of their molecular structures including chemical nature of the end groups (hydroxyl and carboxylate). The compositions of the oligocopolyesters and their sequence distributions were determined based on measurement of the relative intensities of the individual oligocopolyester peaks in the ESI mass spectra. The mass spectra (MS1) provided information on composition and sequence distribution, and small deviations from Bernoulli statistics were detected. The arrangement of co-monomer structural units along the oligopolyester chains was verified by MS/MS experiments and investigation of the fragmentation pathways.

Mass spectra of copolymers which display compositional drifts or sequence constraints.

The spectral features appearing in mass spectra of random and block copolymers which display a drift in composition are discussed along with features appearing in mass spectra of terpolymers and tetrapolymers with sequence constraints. It is shown that previous models cannot account for these features. A new model is presented and a compact equation is derived which yields MS intensities. The prediction of the model is compared with some literature data, namely mass spectrometric data concerning a block copolymer sample containing units of alpha-methyl styrene and of methylmethacrylate which display a strong drift in composition, the molar fraction of methylmethacrylate units changing from 0.99 to 0.80 when passing from short to long macromolecular chains. The agreement between theory and experiment is good. A hyperbranched polymer obtained by condensing 4,4'-bis[p(acetoxy)phenyl] valeric acid (referred to as diphenolic acid, DPA) was then considered. The polymer turned out to be a copolymer with regular DPA units and modified DPA units (possessing a phenol group). The molar fraction of regular DPA units changes from 0.80 to 0.95 when passing from low masses to high masses. Copolymers with sequence constraints are considered, such as ABC copolymers in which AA cannot be found along the chain or ABCD copolymers in which A cannot follow A, B cannot follow B, etc. The novel method is applied to an exactly alternating copolymer with units of styrene (St) and maleic anhydride (MAH). The St-MAH sample turned out to be a complex mixture and the presence of a small amount of units of maleic acid (MAC) is detected. The abundance of MAC, estimated by the chain statistical method, is 5%. The method is applied to the copolymer obtained by reactive blending of poly(butylene terephthalate) and poly(bisphenolA carbonate). In this case, the theoretical spectra are generated and spectral features are discussed.

Is it possible to extend the coleman-fox method for polymer sequence determination by NMR to copolycondensates?

A new theory is presented for the interpretation of NMR spectra of copolycondensates, with special attention to those obtained by melt mixing of two macromolecular chains (reactive blending). The repeat unit is split into two parts, referred to as half-monomers. The present theory gives a highly accurate description of the changes in the sequence distribution during the reactive blending reaction, since the effect of the first and second neighbors along the macromolecular backbone (half-monomer penultimate effect) is explicitly considered. The theoretical predictions are compared with experimental data taken from the literature and, more specifically, NMR data concerning five copolymer systems, namely, a copolymer obtained by reactive blending of poly(ethylene terephthalate) and poly(ethylene adipate), an almost alternating copolymer with units of ether-sulfone and ether-ketone, a copolymer derived from 6-methyl-2,5-morpholinedione, and two copolymers obtained by reactive blending of poly(butylene terephthalate) with poly(bisphenolA carbonate) and Nylon6, respectively.

Mass spectra of copolymers.

Recent and older literature (covering the last 12-13 years) in the field of mass spectra of random and block copolymers is reviewed. A detailed description is given of the information on copolymer properties that can be recovered from the analysis of the low-mass region of the spectrum (the region below 500 Da) and the high-mass region. The features of mass spectra of copolymers obtained by different synthetic routes are discussed, such as free radical, condensation, ring-chain equilibration, microbial synthesis, ring-opening, simple anionic, cationic, Ziegler-Natta, and/or metallocene catalysis, along with some random and block copolymers that occur in Nature. The emphasis is on copolymer composition and average molar mass determination, and on the benefits of coupling mass spectrometry (MS) with separation techniques such as size-exclusion chromatography (SEC) and high performance liquid chromatography (HPLC).