Search

Fluorinated polymers are attractive due to their special thermal, surface, gas separation, and other properties. In this study, new diblock, multiblock, and random copolymers of cyclooctene with two fluorinated norbornenes, 5-perfluorobutyl-2-norbornene and N-pentafluorophenyl-exo-endo-norbornene-5,6-dicarboximide, are synthesized by ring-opening metathesis copolymerization and macromolecular cross-metathesis in the presence of the first- to third-generation Grubbs' Ru-catalysts. Their thermal, surface, bulk, and solution characteristics are investigated and compared using differential scanning calorimetry, water contact angle measurements, gas permeation, and light scattering, respectively. It is demonstrated that they are correlated with the chain structure of the copolymers. The properties of multiblock copolymers are generally closer to those of diblock copolymers than of random ones, which can be explained by the presence of long blocks capable of self-organization. In particular, diblock and multiblock fluorine-imide-containing copolymers show a tendency to form micelles in chloroform solutions well below the overlap concentration. The results obtained may be of interest to a wide range of researchers involved in the design of functional copolymers. [ABSTRACT FROM AUTHOR]

Crystallinity of statistical multiblock copolymers of norbornene and cyclooctene with nearly equimolar composition and different degrees of blockiness is studied by differential scanning calorimetry including thermal fractionation by successive self-nucleation and annealing and by X-ray diffraction. The copolymers are synthesized via recently invented reaction of polymer cross-metathesis, as a result of interchain exchange between polynorbornene and polyoctenamer in the presence of Grubbs’ catalyst of the first generation. This catalyst raises the fraction of trans -octenylene units up to more than 80% promoting formation of triclinic crystals. The copolymer degree of crystallinity and melting peak temperature decrease with the cross-metathesis conversion. At the same time the equilibrium melting temperature predicted by the Flory theory of copolymer crystallization is not much affected by the interchange reaction. Compared with the pure polyoctenamer or its equimolar blend with polynorbornene, the norborene-cyclooctene copolymers form considerably smaller crystallites. Thermal fractionation makes it possible to find their size distribution, which correlates with the average length of trans -octenylene blocks. Short annealing the multiblock copolymers above their melting points gives rise to a small but persistent endotherm 5–10 degrees above the annealing temperature, which is absent in polyoctenamer and, therefore, may indicate mixing of segregated norbornene and cyclooctene blocks. [ABSTRACT FROM AUTHOR]

Commercial metathesis polynorbornene is used for the fabrication of high-damping coatings and bulk materials that dissipate vibration and impact energies. Functionalization of this non-polar polymer can improve its adhesive, gas barrier, and other properties, thereby potentially expanding its application area. With this aim, the post-modification of polynorbornene was carried out by inserting ethylene–vinyl acetate–vinyl alcohol blocks into its backbone via the cross-metathesis of polynorbornene with poly(5-acetoxy-1-octenylene) and subsequent deacetylation and hydrogenation of the obtained multiblock copolymers. For the first time, epoxy groups were introduced into the main chains of these copolymers, followed by the oxirane ring opening reaction. The influence of post-modification on the thermal, gas separation, and mechanical properties of the new copolymers was studied. It was shown that the gas permeability of the copolymer significantly depends on its composition, as well as on the amounts of hydroxyl and epoxy groups. The developed methods efficiently improve the barrier properties, reducing the oxygen permeability by 15–33 times in comparison with polynorbornene. The obtained results are promising for various applications and can be extended to a broader family of polydienes and other polymers containing backbone double bonds. [ABSTRACT FROM AUTHOR]

We investigate the structure–property relations of the multiblock copolymers of norbornene with cyclododecene synthesized via the macromolecular cross-metathesis reaction between amorphous polynorbornene and semicrystalline polydodecenamer in the presence of the first-generation Grubbs catalyst. By adjusting the reaction time, catalyst amount, and composition of the initial system, we obtain a set of statistical multiblock copolymers that differ in the composition and average length of norbornene and dodecenylene unit sequences. Structural, thermal, and mechanical characterization of the copolymers with NMR, XRD, DSC (including thermal fractionation by successive self-nucleation and annealing), and rotational rheology allows us to relate the reaction conditions to the average length of crystallizable unit sequences, thicknesses of corresponding lamellas, and temperatures of their melting. We demonstrate that isolated dodecenylene units can be incorporated into crystalline lamellas so that even nearly random copolymers should retain crystallinity. Weak high-temperature endotherms observed in the multiblock copolymers of norbornene with cyclododecene and other cycloolefins could indicate that the corresponding systems are microphase-separated in the melt state. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multiblock PNB–PCP copolymers were synthesized by cross-metathesis. • Inclusion of CP units into copolymer is hampered by PCP depolymerization. • Polymer concentration during the reaction determines the copolymer chain structure. • Other key factors are type of the catalyst and temperature. • Copolymer hydrogenation allows to reveal the details of its structure. Statistical multiblock copolymers of norbornene (NB) and cyclopentene (CP) with different compositions and average block lengths are synthesized via the metathesis of polynorbornene (PNB) with polypentenamer (PCP) mediated by Grubbs' catalysts of the 1st (G1) and 2nd (G2) generations. Interest in the copolymerization of NB and CP is dictated by the attractive properties of their homopolymers, whereas its realization is hampered by the mismatch in their metathesis polymerization activities. This difficulty can be circumvented by starting from the homopolymers, which are well-known industrial products. Our study demonstrates that the interaction of PNB with PCP in dilute solutions at room temperature in the presence of G1 leads to the copolymers with short CP blocks of 1–3 units separating longer NB blocks. In situ 1H NMR monitoring of the process reveals nearly full depolymerization of PCP via the ring-closing intramolecular metathesis and the formation of NB–CP copolymers presumably via the interaction of CP with PNB. The depolymerization can be suppressed by increasing the concentration of reacting polymers and replacing G1 with more active G2. Under these conditions, the cross-metathesis of PNB with PCP results in the multiblock NB–CP copolymers with composition close to that of the initial homopolymer mixture, but short blocks of the both comonomers. A copolymer with longer blocks that can inherit properties of the parent homopolymers is obtained by decreasing the reaction temperature to 5 °C. Additional information about the structure of NB–CP copolymers is obtained via their hydrogenation followed by spectral and thermal characterization. Thus, the macromolecular cross-metathesis of unsaturated polymers appears to be a versatile method to synthesize copolymers with different backbone structures that are hard to reach by other methods. [ABSTRACT FROM AUTHOR]

Cross-metathesis of 5-hydroxycyclooctene and norbornene homopolymers affords the multiblock copolymer possessing a broad range in the degree of blockiness (from 0.03 to 1). [ABSTRACT FROM AUTHOR]

Bulkand solution studies revealed a strongly pronounced effect of chainstructure on the rheological and relaxation behavior of well-characterizedvinyl acetate–vinyl alcohol copolymers of similar compositionand polymerization degree. The frequency–temperature superpositionprinciple is fully applicable to the random copolymers, which demonstrateall expected relaxation states, whereas a divergence of the reduceddynamic moduli–frequency dependences is observed for the multiblockcopolymers. In the latter case, the terminal zone is sensitive tothe self-assembling of vinyl alcohol blocks into (depending on thecopolymer composition) crystalline or amorphous microstructures. Themonomer unit distribution particularly affects properties of the copolymersolutions in N,N-dimethylformamide(DMF). 5% solutions behave as simple viscoelastic liquids at 20 °Cand show viscoplastic behavior at −20 °C, where more blockychains are characterized by up to 4 orders of magnitude higher yieldstress values. The multiblock copolymer solutions demonstrate a pronouncedviscosity hysteresis in the heating–cooling cycle, being absentin the random copolymers. 10% solutions of multiblock copolymers arepractically gelatinous even at room temperature. The observed effectsare explained by examining the peculiarities of hydrogen bonding invinyl acetate–vinyl alcohol copolymers using FTIR spectroscopy.The multiblock copolymers are characterized by stronger hydroxyl–hydroxylH-bonds and greater fraction of interchain hydroxyl–acetyloxyH-bonds providing aggregation of chains and high viscosity of thecorresponding samples, whereas the random copolymers more stronglyinteract with the residual solvent. Dynamic light scattering studiesprove that the relaxation of concentration fluctuations is completelydiffusive, being bimodal in the random copolymers and trimodal inthe multiblock ones. The fast mode in the latter case demonstratesanomalous concentration behavior. In the dilute regime, up to verylow concentrations, multiblock copolymer chains form stable aggregates,and this fact correlates with an unusual growth of the reduced viscosityin the corresponding rheological experiments. [ABSTRACT FROM AUTHOR]