Supramolecular polymerization, i.e., the self-assembly of polymer-like materials through the utilization of the noncovalent bond, is a developing area of research. In this paper, we report the synthesis and investigation of nucleobase-terminated (N6-anisoyl-adenine and N4-(4-tert-butylbenzoyl)cytosine) low molecular weight poly(THF) macromonomers (<2000 g mol(-1)). Even though the degree of interaction between the nucleobase derivatives is very low (<5 M(-1)) these macromonomers self-assemble in the solid state to yield materials with film and fiber-forming capability. While the mechanical properties of films of both materials show extreme temperature sensitivity, resulting in the formation of very low viscosity melts, they do behave differently, which is attributed to the nature of the self-assembly controlled by the nucleobase. A combination of FT-IR, WAXD, and rheological experiments was carried out to further investigate the nature of the self-assembly in these systems. The studies demonstrate that a combination of phase segregation between the hard nucleobase chain ends and the soft poly(THF) core combined with aromatic amide hydrogen bonding is utilized to yield the highly thermosensitive supramolecular polymeric materials. In addition, analysis of the data suggests that the rheological properties of these supramolecular materials is controlled by the disengagement rate of the nucleobase chain ends from the "hard" phase, which, if shown to be general, provides a design criteria in the development of more thermally responsive materials.

Polymandelide, an aryl analogue of polylactide, was synthesized by the ring-opening polymerization of mandelide, the cyclic dimer of mandelic acid. The poor solubility of rac-mandelide limited the synthesis of polymandelide via solution polymerization, but polymerization of mandelide at 70 °C as a heterogeneous slurry in acetonitrile yielded first-order kinetic plots and polydispersities <1.2. High molecular weight polymer prepared by melt polymerizations at T > 150 °C exhibit properties that mimic those of polystyrene. Polymandelide is a glassy amorphous polymer with a T g of 100 °C, with rheological properties comparable to polystyrene, and thermal gravimetric analyses under nitrogen show that the polymer is stable to ∼300 °C. Racemization during polymerization precluded formation of a crystalline polymer. Degradation of polymandelide in pH 7.4 buffer at 55 °C is consistent with a bulk erosion model and, due to its high T g , proceeds at ∼1/100 the rate of polylactide under similar conditions.

Smart materials comprising natural and/or synthetic polymers and designed for application in aqueous environments that require minimal protein adsorption 1 smarine coatings, nanocarriers for drug delivery, scaffolds for tissue engineering, etc.shave seen a rapid rise in their investigation. These materials commonly have hydrophilic, hydrogel characteristics and properties (e.g., low mechanical strength) that introduce difficulties in handling and may impede their biological uses. 1,2 Our interest in the development of nontoxic, antibiofouling marine coatings requires mechanically robust or tough materials, both in the dry state and in the marine environment. These coatings rely upon limiting bioadhesion, which depends on the surface energy, 3 surface reconstruction, 4 and other properties of the materials, 5 including the elastic modulus. 6 Recently, an amphiphilic crosslinked polymer network, composed of hyperbranched fluoropolymer and poly(ethylene glycol) (HBFP-PEG), has been developed with complex surface topographies, morphologies, and compositions distributed over nanoscopic dimensions. 7 Importantly, this complex material has exhibited superior abilities to inhibit protein adsorption and prevent marine organism settlement, which are related to its composition, 8 its heterogeneous surface properties, and the resulting surface reconstruction under water. 4a,7 In addition, the subsurface morphology provides nanoscale channels that have been shown to serve as a host environment for the uptake and promoted release of guest molecules. 7c Because of the potential utility of the unique surface and subsurface properties of these materials, in applications that involve an aqueous environment, we have now investigated their mechanical properties, as prepared and after swelling in water. The stoichiometry of the HBFP and PEG were varied to alter the relative hydrophobic/hydrophilic balance and to control the domain sizes enriched in each of these two components. Interestingly, unlike hydrogels, water molecules were found to rigidify the amphiphilic networks, composed of a minority of PEG, whereas absorption of water molecules afforded the opposite effect when the materials were comprised of a PEG majority.The amphiphilic networks were prepared and characterized as described previously. 7 The labile p-fluorine of the pentafluorophenyl groups present within HBFP (M n ) 9000 Da) underwent nucleophilic substitution by the terminal amino groups of bis(3-aminopropyl)-terminated PEG (M n ) 1600 Da) to interconnect the two immiscible components (Scheme S1 of Supporting Information (SI)), upon casting from tetrahydrofuran solution onto chlorotrimethylsilane-treated glass microscope slides. Such in-situ crosslinking trapped the thermodynamically driven phase segregation kinetically to provide nanoscopic features on the surface and throughout the bulk of the material. 7 The tensile properties of four systems, HBFP-PEG30, HBFP-PEG45, HBFP-PEG55 and HBFP-PEG63 (containing 30, 45, 55, and 63 wt % of PEG, respectively) were the...

Novel nanocomposites possessing ternary compositions and complex morphologies have been prepared from amphiphilic crosslinked hyperbranched fluoropolymer–poly(ethylene glycol) (HBFP–PEG) in the presence of pristine and chemically functionalized nanoscopic fillers, single‐walled carbon nanotubes (SWNTs) and silica nanoparticles (SiO2). Both SWNTs and SiO2 were engineered specifically to become phase‐designated reinforcing functional materials, SWNT‐g‐PEG and SiO2‐g‐HBFP, which (1) improved the dispersion of fillers, nanotubes, or spherical nanoparticles in the amphiphilic matrices, (2) enhanced the non‐covalent interactions between nanofillers and polymers, and more importantly, (3) maintained reactive functionalities to be further covalently integrated into the complex networks. Tensile moduli (Edry) for these as‐prepared SWNT‐containing composites increased by up to 430% relative to the unfilled material, while those incorporated with SiO2 had a 420% increase of Edry. After swelling in water, the water absorption within the micro‐ and nanochannels of PEG‐rich domains rigidified or softened the entire crosslinked network, as determined by the amount of PEG.