Poly(ethylene terephthalate)–poly(lactic acid) (PET–PLLA) copolyesters were synthesized by the melt reaction of bis(2-hydroxyethyl terephthalate) (BHET) with
l-lactic acid oligomers (OLLA) in the ...presence of SnCl
2, H
2O–
p-toluene sulfonic acid, H
2O catalytic system. The
1H and
13C NMR studies confirm the incorporation of lactate units in PET chains after reaction. Copolyesters containing nearly equimolar terephthalate/lactate ratio are not completely random and present some block-copolymer character, while the microstructure of PET-rich copolyesters is a random one. Due to a longer PET sequence length, the latter exhibit a melting point close to 210
°C while the other ones are amorphous. SEC/MALDI-TOF MS off-line coupling was used to obtain the absolute average molar masses of the copolyesters. The results indicate that the conventional polystyrene calibration method leads to a strong overestimation of PET–PLLA molar masses, while the
M
n
¯
determined by NMR is much closer to the SEC/MALDI value.
Extraction of cellulose type I nanocrystals from cotton fibers was straightforwardly carried out using exclusively Brønsted acid-type ionic liquids (ILs) via a two-step swelling/hydrolysis route, the ...switch between these two stages being induced by water addition. Since the whole process was achieved in a single reaction medium predominantly based on 1-butyl-3-methylimidazolium chloride (BMIMCl) and 1-(4-sulfobutyl)-3-methylimidazolium hydrogen sulfate (SBMIMHSO
4
), the process parameters were investigated in order to ensure a perfect compatibility and sequencing towards the two-step route proposed here. The impacts on nanoparticle morphology, crystallinity evolution, and cellulose type I to type II denaturation were observed under field-emission gun scanning electron microscopy and corroborated by X-ray diffraction characterizations. ILs recovery and reuse were also demonstrated, opening up new prospects of conception of multi-cycle, environmentally and economically sustainable processes.
The absolute average molar masses and polydispersity index of a series of polyesters based on 2,2-bis(hydroxymethyl)propanoic acid (BMPA, AB2-type monomer), 2,2-bis(hydroxymethyl)-1,3-propanediol ...(PE, B4-type monomer), and 1,1,1-tris(hydroxymethyl)propane (TMP, B3-type monomer) were determined by SEC/MALDI−TOF off-line coupling. The M̅ w /M̅ n values, in the 1.8−3.1 range, were surprisingly very close to those found by SEC using the conventional linear polystyrene calibration method, but dramatically lower than those calculated from conversion and composition of initial monomer mixture assuming equal reactivity of functional groups. The mol ratios of the various monomer units in final polyesters were determined by 13C NMR. The kinetic-recursive probability approach assuming first-shell substitution effects was then applied to calculate the branching factors and the average molar masses of these polyesters from their final composition. The AB- and B-branching factors were significantly lower than expected for random polymerizations, reflecting the existence of both negative A−B and B−B substitution effects, i.e. lower reaction rate of a given A or B group after reaction of the other groups present on the same monomer unit. The calculated values of M̅ w and M̅ w /M̅ n were reasonably close to the experimental ones for all hyperbranched polyesters. Intramolecular esterifications and intermolecular etherifications side reactions were taken into account in the calculations with some simplifying assumptions and found to marginally broaden MW distributions.
Poly(β-alanine) was successfully synthesized by an alternative method, which is the direct polyamidation of β-alanine in ionic liquids with triphenylphosphite as a condensing agent. It was found that ...1,3-dimethylimidazolium dimethylphosphate was the most suitable reaction medium, in which a number-average degree of polymerization up to 49.5 was obtained. It was shown that the method is also applicable to the direct synthesis of polypeptides, for example, poly(l-valine) and poly(l-isoleucine).
A series of polyamides based on Z‐octadec‐9‐enedioic acid, a bio‐based unsaturated monomer, and aliphatic‐, cycloaliphatic‐, or benzylic diamines were synthesized and characterized by 1H and 13C NMR ...analysis, size exclusion chromatography (SEC), DSC, and dynamic‐mechanical analysis (DMA). The high reaction temperature (250 °C) did not lead to the degradation of diacid unit double bonds and unsaturated polyamides were obtained. The aliphatic unsaturated polyamides are semi‐crystalline polymers of high molar mass, relatively flexible at room temperature. The cycloaliphatic unsaturated polyamides are semi‐crystalline or amorphous, present higher melting and glass transition temperatures and are much more rigid. The aliphatic and aliphatic–aromatic unsaturated polyamides present lower Tg and Tm as compared to their parent saturated polymers.
This document provides (i) definitions of terms related to macromolecular rotaxanes and macromolecular pseudorotaxanes and (ii) recommendations for naming these macromolecular assemblies. The ...nomenclature recommendations presented here have been developed by combining the nomenclature rules for the low-molar-mass (low-M) rotaxanes and those for macromolecules (both established in published IUPAC recommendations) in such a way that the developed nomenclature system provides unambiguous names for macromolecular rotaxanes (and pseudorotaxanes), including differentiation among various isomers of these supramolecular assemblies. Application of the nomenclature recommendations is illustrated using examples covering a wide range of structure types of macromolecular rotaxanes and pseudorotaxanes. An Alphabetical Index of Terms and a List of Abbreviations and Prefixes are included.
Bulk reactions of phenolic compounds (bisphenol-A and α,ω-diphenol oligosulfone) or thiols (thiophenol and bis(4-mercaptophenyl)sulfide) with bisoxazoline coupling agents, namely ...2,2'-(1,3-phenylene)bis(2-oxazoline) (mbox), 2,2'-(1,4-phenylene)bis(2-oxazoline) (pbox), and 2,2'-(2,6-pyridylene)bis(2-oxazoline) (pybox), were carried out in the bulk at 140-240°C. The reactions were followed by viscosimetry, size exclusion chromatography, and ¹H- and ¹³C-NMR spectroscopy. The phenol/bisoxazoline bulk reactions at 240°C required the presence of sodium methoxide catalyst. Bisoxazoline pybox gave the best results in this case. Thiol and dithiol/bisoxazoline reactions were faster and did not require any catalyst. High-molar-mass polymers were obtained within 5 min at 200°C while using bis(4-mercaptophenyl)sulfide (BMPS) and any of the bisoxazolines. The NMR spectra of model compounds and polymers were fully assigned, showing that the oxazoline/phenol and oxazoline/thiophenol (tph) polyaddition reactions proceed in the expected way, without any noticeable side reaction. All polymers were amorphous and displayed good thermal stability. Bisoxazolines were also used as coupling agents for the preparation of copolymers of BMPS and α,ω-dicarboxy polyamide-12 and for the preparation of polysulfone-polyamide-12 block copolymers.
PDF
