A new source-based nomenclature system is described which indicates that a particular polymer has been chemically modified. A connective within the name of a polymer, -
-, is introduced for this ...purpose as in poly(A)-
-(B). The system is intended to be used in accordance with source-based naming of polymers but also provides for the use of structure-based names when it is unavoidable. It embraces: (1) modification of a constitutional unit into another, the unique structure of which is known; and (2) a more general modification of a constitutional unit resulting in any one of a number of possible structures. In addition, a new symbol, ∼>, is proposed for use in graphic representations of the structure of modified polymers.
5,5′‐Isopropylidene‐bis(ethyl 2‐furoate), a monomer prepared from bio‐based ethyl 2‐furoate, was reacted with dimethyl terephthalate and ethan‐1,2‐diol (ED) by melt polycondensation in order to ...obtain copolyesters containing both terephthalate and furoate units. The conventional two‐step method involving (i) the formation of a hydroxyethyl‐terminated oligomer by reaction of starting diester mixture with excess ED and (ii) a polycondensation step with elimination of ED was used to obtain high molar mass copolyesters. Copolymers of various compositions were synthesized and characterized by 1H NMR, DSC, and TGA. For all compositions, the degree of randomness, determined by 1H NMR, was close to 1, reflecting a random distribution of terephthalic and furanic ester units in polymer chains. The resulting materials are amorphous polymers (Tg = 70–80 °C) with good thermal stability.
Hyperbranched Poly[bis(alkylene)pyridinium]s Monmoton, Sophie; Lefebvre, Hervé; Costa-Torro, France ...
Macromolecular chemistry and physics,
December 1, 2008, Letnik:
209, Številka:
23
Journal Article
Recenzirano
3,5‐Bis(bromomethyl)pyridine hydrobromide and 3,5‐bis(bromobutyl)pyridine hydrobromide were synthesized from commercially available 3,5‐lutidine. The poly(N‐alkylation) of these monomers readily ...yielded new hyperbranched polyelectrolytes. The progress of reaction was followed by 1H NMR. A second‐order kinetic scheme fits the experimental data. Rate constants and activation parameters were determined, showing the higher reactivity of 3,5‐bis(bromomethyl)pyridine hydrobromide. This was explained by the electron‐attractive effect of pyridinium groups on the CH2Br end groups. The structures of the hyperbranched poly3,5‐bis(alkylene)pyridiniums were investigated by 1H and 13C NMR spectroscopy and a preliminary study of their properties is reported.
The bulk reactions between carboxy‐terminated polyamide‐12 (PA12) or carboxy‐terminated poly(butane‐1,4‐diyl adipate) (PBDA) and 2,2′‐(1,3‐phenylene)bis(2‐oxazoline) (mbox), ...2,2′‐(1,4‐phenylene)bis(2‐oxazoline) (pbox), 2,2′‐(2,6‐pyridylene)bis(2‐oxazoline) (pybox) as chain‐coupling agents were studied by size exclusion chromatography, carboxy end‐group titration, and NMR spectroscopy. The chain‐coupling reaction yielded high‐molar mass polymers within 20 to 180 min, depending on reaction temperature, starting oligomer molar mass, bisoxazoline/oligomer molar ratio, and the nature of bisoxazoline. No side‐reactions were observed. Bisoxazoline pybox, used for the first time in the bulk chain extension of carboxy‐terminated polymers, exhibited the highest reaction rates. The thermal properties of the resulting polymers, studied by differential scanning calorimetry and thermogravimetric analysis, are also discussed.
The reaction of PBDA and PA12 with mbox, pbox, and pybox to give rise to the polymers studied here.
Kinetic studies of the reactions between a model carboxylic acid and 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 bulk at 140–220 °C. A second‐order two‐step reaction mechanism was proposed and was verified by the experimental results. The results also indicate that the reactivity of the oxazoline groups is unchanged after the reaction of the other oxazoline group of the same coupling agent moiety, that is, oxazoline groups are equireactive. Rate constants and activation enthalpies and entropies were determined, allowing the comparison of bisoxazoline reactivity. The following reactivity order was found: pybox > mbox > pbox. The formation of a stabilized protonated complex is postulated to explain the much higher reaction rate observed with the new coupling agent pybox.
Variation of the experimental concentrations of reactants and reaction products versus time.
Bis{4-2-(2,3-epoxypropyl)ethoxybenzoate}-1,4-phenylene and bis4-(2,3-epoxypropoxy)benzoate-methyl-1,4-phenylene liquid crystalline diepoxy monomers were crosslinked with various diamines in a ...magnetic field. X-ray scattering was used for mesophase identification and to determine the nematic order parameter of the resulting thermosets, which were cured under various temperature and magnetic field strength conditions. All thermosets exhibited nematic or smectic A (SmA) mesophases. The thermosets obtained from aliphatic diamines exhibited a very low degree of orientation. This phenomenon was assigned to their high reactivity, inducing a very fast crosslinking reaction that prevents the alignment of the mesogens. On the other hand, very high degrees of orientation along the magnetic field axis were observed for the SmA thermosets. In this case, the smectic period was smaller than the length of the epoxy monomer unit, which might be due to a staggered packing of the mesogenic cores. Negative longitudinal thermal expansion coefficients were measured below and above the glass transition temperature for the materials cured in a magnetic field.
The solution polymerization of 4‐bromomethylpyridine (M1) and 3‐bromomethyl pyridine hydrobromides (M2) was studied by NMR spectroscopy. A mechanism involving a series of bimolecular reactions of the ...monomer, dimer, and higher oligomers closely fits with the experimental variations of bromomethyl end group concentrations with time. M1 presents a higher reactivity than M2 and an unusual behavior, since the oligomers are more reactive than the monomer. An explanation based on a mesomeric phenomenon is proposed. The influence of the anion on the solubility and thermal stability of the poly(methylenepyridinium)s were studied after various anion exchanges. Bis(trifluoromethylsulfonyl)imide anion (Tf2N) yielded the more stable and the more organosoluble polymers.
Aromatic copolyesters containing bio‐based furanic units in the main chain were obtained by ester‐interchange reaction between poly(ethylene terephthalate) (PET) and polyethylene ...5,5′‐isopropylidene‐bis(2‐furoate) (PEF) at high temperatures in the bulk. Various copolyesters were synthesized by using PET/PEF mass ratios ranging from 90:10 to 50:50 and were characterized by 1H NMR, MALDI‐TOF MS, DSC, and TGA. PET/PEF block copolymers were formed in the first stage of reaction and then slowly randomized. The degree of randomness, determined by 1H NMR, was close to 1 after 2 h reaction. The randomization rate depended on the nature and the concentration of the end‐groups of starting homopolyesters and was much faster when a low molar mass hydroxy‐terminated PET was reacted.
Reaction scheme showing the insertion of furanic units in copolyester chains by ester interchange reaction.
