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Diol-functionalized trisaminocyclopropenium (TACP) carbocations were used as chain extenders in a two-step synthesis of a segmented polyurethane. Differential scanning calorimetry demonstrated significant differences in the crystallization behavior of the poly(tetramethylene oxide) soft segment when minor changes were made to the TACP structure and when compared to a control that was chain extended with butane diol. Fourier transform infrared spectroscopy was used to characterize the different level of hydrogen bonding in the polymers and showed that the bulky, charged TACP chain extender limited hydrogen bonding interactions when compared to the control. Dynamic mechanical analysis was used to probe the thermomechanical behavior of polymers that showed that the TACP-containing polymers were much more resistant to flow at high temperatures when compared to the control. Small-angle X-ray scattering showed a phase separated morphology for all the polymers tested. Tensile testing of the TACP polyurethanes demonstrated an elastic response over a wide range of strain, followed by a significant strain hardening. These results suggest a morphology of ionic aggregates rather than hard segment physical cross-links.

Fluorinated molecules containing reactive functionalities are of great interest to the materials community as these compounds can be used to prepare fluorinated polymers with desirable physical and electronic properties. Despite their potential, many of these compounds are limited by their synthesis which generally requires transition-metal-catalyzed coupling reactions or harsh fluorinating conditions. Perfluoroheteroaromatic compounds provide a unique solution to this problem as compounds such as perfluoropyridine can undergo S

Understanding multicomponent diffusion in polymers on the molecular-scale could lead to optimization of many practical processes. One important example is the removal of a toxic chemical (penetrant) from polyurethanes, which serve as the binder in many coatings technologies. This work is an equilibrium molecular dynamics (MD) study to characterize the molecular-scale hydrogen bonding (H-bonding) interactions in ternary penetrant, solvent, and polyurethane systems, and how these H-bonds influence the corresponding diffusivities. Homomorphic series of penetrant and solvent species in which molecular size and shape are kept constant while varying polarity or number of H-bonding sites are used to study the influence of hydrogen bond probability and strength on diffusivity. It is found that H-bonding between all species in the ternary mixture as well as penetrant-solvent collisions play a role in determining penetrant diffusivity. The findings provide insight into solvent selection criteria to increase the diffusivity of H-bonding penetrants that are absorbed in polyurethanes for extraction and decontamination applications.

This work investigated the morphological behavior of an acrylate-based metallo-supramolecular polymer system. RAFT (reversible addition–fragmentation chain transfer) polymerization techniques were used to synthesize low molar mass, linear prepolymers of n-butyl acrylate and a 2,6-bis(1′-methylbenzimidazolyl)pyridine–acrylate monomer (MeBIP–Ac) of varying concentration (2–10%). This synthesis incorporated a systematic increase of cross-link points (MeBIP ligands) pendent to the polymer backbone. A zinc(II) salt (Zn(ClO4)2) complexed with the pendent MeBIP ligands in a 1:2 ratio to form cross-linked polymers as free-standing films. The morphology of the neat films as well as those with added unbound MeBIP–zinc–MeBIP metal–ligand (ML) complex were characterized using transmission electron microscopy (TEM), HAADF-STEM (high angle annular dark field scanning transmission electron microscopy), energy dispersive X-ray spectroscopy (EDS), electron energy loss spectroscopy (EELS), energy-filtered TEM (EFTEM), and ...

This work incorporates ML complexes as unbound entities that interact with ML complexes bound to the backbone of the polymer. The π–π interactions and Coulombic forces between bound and unbound ML complexes hold the ML-rich phase together and result in improved mechanical properties over polymers containing only the bound ML complexes. The ML-rich phase formed ordered, cylindrical domains. The storage modulus, surface elastic modulus, and high temperature stability of these metallopolymers increased with increasing concentration of ML complex in the polymer while an optimal concentration and morphology are necessary to improve the strength and creep resistance of the polymer. Ultimately, the successful addition and patterning of unbound ML complexes as a hard phase in a polymer matrix provides an important template for the design of a new type of supramolecular nanocomposite.

Epoxies and polyurethanes are both important classes of materials with wide-ranging applications. The merging of both chemistries presents new opportunities to investigate materials with potentially unique or improved performance. In this work, a series of formulations with varying levels of epoxy and cyclic carbonate monomers were reacted with a multifunctional amine to produce network polymers with hybrid functionality. The spectroscopic, swelling, thermal-mechanical, tensile, and adhesive behaviors were evaluated. The materials performed as expected based on the proposed network structure as determined through small-molecule model studies. In particular, the hybrid network polymers performed admirably as adhesives with significantly improved performance over an epoxy–amine control.

Evaluation and prediction of multicomponent diffusion in polymers is an important area of research since it occurs in several fields associated with mass transport including membrane separations, preparation of polymer films, and material decontamination. The functional dependence of the diffusivity on the composition in a multicomponent system is critical for accurately predicting transport in these processes. Here, the composition dependent diffusivity of 2,5-lutidine in polyurethane with acetonitrile as a co-penetrant was experimentally determined using Fourier transform infrared spectroscopy (FTIR) to acquire differential sorption curves for lutidine across the composition space and fitting a multicomponent diffusion model to the data. The free volume theory of diffusion was used to develop a mathematical expression for the composition-dependent diffusivity, and shows good agreement with the experimental data for both single and multicomponent cases. The lutidine diffusivity was found to vary up to two orders of magnitude with ACN concentration, and the importance of capturing this dependence quantitatively is highlighted by applying the multicomponent diffusion model with the best-fit values to predict previously published data for lutidine desorption from polyurethane.

The organocatalyzed aminolysis of cyclic carbonates to form (poly)hydroxyurethanes is an important reaction as an alternative to isocyanate based chemistries. In an effort to increase reaction rates between cyclic carbonates and amines to lower cure times and increase molecular weights, various organocatalysts were surveyed. Reaction rates between monofunctional model cyclic carbonates and amines were determined in the presence of a variety of organocatalysts, which operate under different mechanisms to promote the reaction. Of the catalysts investigated, TBD was the most potent, presumably due to its bifunctional activity. TBD was also used to promote step-growth polymerization between difunctional cyclic carbonates and amines. The polymers produced in the presence of TBD at room temperature were much higher in molecular weight than polymers produced in the absence of catalyst at both room temperature and at 80 °C.

This work studies the properties of poly(n-butyl acrylate) functionalized with 2,6-bis(1′-methylbenzimidazolyl)pyridine ligand and cross-linked with either copper(II), zinc(II), or cobalt(II) metal ions. Because of phase separation between the metal–ligand complex and the polymer matrix, these polymers have a rubbery plateau modulus that is 10 times higher than expected based on the theory of rubber elasticity. Differences in the metal–ligand bond strength influence the mechanical behavior at high temperature and strains. Because of the particularly weak bond strength associated with the copper–ligand bond, the metallopolymer containing copper degrades at a lower temperature and has lower yield strength, ultimate tensile strength, and creep resistance than polymers containing cobalt and zinc. To tune the properties of the polymer further, a polymer is made with both copper and cobalt ions. The hybrid polymer combines the properties of the stiffer cobalt-containing polymer with the more compliant copper-co...

Methods for removing the residual Grubbs' third generation catalyst from polymers prepared by ring opening metathesis polymerization are reported. Two strategies were investigated for reduction of the residual catalyst in the final polymer product. The first strategy involved the use of heterogeneous functionalized particles to scavenge the catalyst from the solution. Filtration of the particles followed by precipitation produced polymers with 10–60 ppm residual catalyst, depending on the type of particle used, surface functional groups, and number of equivalents. The second strategy used small organic molecules that could coordinate to the metal species and modify the solubility of the catalyst, facilitating partitioning of the catalyst into the precipitation solvent. Several types of molecules with varied functionality reduced the residual catalyst level to 30–120 ppm, depending on the loading. Hydrogenation of the polymer backbone followed by precipitation lowered the residual Ru content from 195 ppm to 10 ppm, suggesting that the difficulty of completely removing the catalyst could be a result of coordination of the metal species to the double bonds in the polymer backbone. Reducing the amount of trace catalyst significantly improved the oxidative stability of the polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

A method for producing well-defined azobenzene functionalized polymers via ring-opening metathesis polymerization (ROMP) is described. ROMP of an isomerically pure exo-norbornene ester tethered to an azobenzene unit in the presence of the third generation Grubbs' catalyst was investigated in detail. The polymerization was determined to be living on the basis of a linear relationship between Mn and [M]/[I] and the ability to quantitatively produce chain extended homopolymers. The polymer's physical response to plane-polarized light was studied in thin films and latex particles. A relief grating was inscribed on the surface of a thin film by irradiation with an interference pattern of linearly polarized light. The same material was used to prepare isotropic colloidal particles of the polymer. These latex particles were transformed to ellipsoids in response to irradiation by linearly polarized light perpendicular to the sample surface.

A highly stereoselective Saucy–Marbet rearrangement using chiral ynamides and propargyl alcohols is described here. This rearrangement can be catalyzed by para-nitrobenzenesulfonic acid and leads to high diastereoselectivities for a range of different chiral propargyl alcohols and ynamides in a stereochemically intriguing matched, mismatched or indifferent manner. The stereoselective Saucy–Marbet rearrangement of ynamides provides an excellent entry to highly substituted chiral homo allenyl alcohols.

A simple and facile preparation of chiral and bis-pyrroles is described here. This method involves a modified Paal-Knorr reaction using 1,4-dicarbonyl systems derived from ozonolysis of allylated β-ketoester.

We present a detailed investigation of the aminolysis of six-membered cyclic carbonates to form (poly)hydroxyurethanes. Model reactions between hexyl amine and trimethylene carbonate were performed under different conditions where we surveyed the effects of temperature and the presence of catalyst on the rate of reaction. Increased temperatures and the presence of catalyst lead to significant increases in the rate of reaction and overall conversion depending on the structure of the catalyst. Similar observations were also made in model polymerization between a carbonate derivative of di(trimethylolpropane) and diaminopentane. However, the increased rates of reaction and conversion only lead to modest gains in molecular weight. In addition, gelation of the polymerization mixture often occurred as well. Nominal and High resolution mass spectrometry were used to identify side products which formed during the reaction between trimethylene carbonate and hexyl amine which explained the gelation of polymerization mixture and lower than expected molecular weights. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44941.

[reaction: see text] A highly stereoselective Saucy-Marbet rearrangement using chiral ynamides and propargyl alcohols is described here. This rearrangement can be catalyzed by para-nitrobenzenesulfonic acid leading to high diastereoselectivities for a range of different chiral propargyl alcohols and ynamides in a stereochemically intriguing matched, mismatched, or indifferent manner. This provides an excellent entry to highly substituted chiral homoallenyl alcohols.