Combinations of Microphase Separation and Terminal Multiple Hydrogen Bonding in Novel Macromolecules

Abstract

The synthesis and characterization of terminal multiple hydrogen-bonded (MHB) polymers, such as poly(styrene) (PS), poly(isoprene) (PI), and microphase separated PS-b-PI block copolymers, possessing controlled molecular weights and narrow molecular distributions are described. Hydroxyl-terminated polymeric precursors were prepared using living anionic polymerization and subsequent quantitative termination with ethylene oxide. MHB polymers were synthesized in a controlled fashion via end-group modification of these well-defined macromolecular alcohols with excess isophorone diisocyanate and subsequent derivatization of the isocyanate-terminated polymeric intermediate with methyl isocytosine. The glass transition temperatures of the terminal MHB polymers were reproducibly higher than both nonfunctionalized and hydroxyl-terminated polymers at nearly equivalent number average molecular weights. Thin-layer chromatography analysis indicated that the interaction of terminal MHB polymers with silica was stronger as compared to both nonfunctionalized and hydroxyl-terminated polymers. Rheological characterization indicated that the melt viscosity at constant shear rate for various MHB polymers was more than 100 times higher than those for nonfunctionalized and hydroxyl-terminated polymers. Interestingly, the melt viscosity of MHB polymers was higher than those of nonfunctionalized polymers with twice the number average molecular weight. In addition, DSC and rheological characterization also suggested that terminal MHB polymers formed aggregates and not simple dimers in the melt state, and the aggregates were observed to completely dissociate at 80 degrees C.

Supramolecular Biomaterials. A Modular Approach towards Tissue Engineering

“…68 Furthermore, the group of van Hest showed the synthesis of nucleobase-functionalized block copolymers via atom-transfer radical polymerization of thymine, adenine, cytosine, and guanine nucleobase-functional methacrylates. 69,70 The quadruple hydrogen-bonding UPy-unit, developed in our group, has been further employed in the functionalization of several low molecular weight polymers, such as poly-(dimethylsiloxanes) (PDMS), 41,71 poly(ethylene butylenes) (PEB), [72][73][74] poly(ethers), 72,75,76 poly(carbonates), 72,77 poly-(styrenes) (PS), 78 poly(isoprenes) (PI), 78 poly(ethylene-copropylenes) (PE-co-PP), 79 and poly(esters) 28,72,80,81 (Table 1). a) The compound numbers correspond to the numbers in Fig.…”

“…These viscosities were more than 100 times higher than the unfunctionalized polymers. 78 In addition, differential scanning calorimetry and rheological characterization suggested the formation of aggregates, and not simple dimers, in the melt state. Also, poly(ethylene-co-propylene) prepolymers were coupled to UPy-units.…”

Phase Behavior of Complementary Multiply Hydrogen Bonded End-Functional Polymer Blends

“…19 The nature of the interaction varies widely and most commonly consists of either metal-ligand, 20,21 ionic, 22,23 or hydrogen bonding. 24,25 Incorporation of these into various macromolecular architectures such as diblock, [26][27][28][29][30][31][32][33][34][35] triblock, [36][37][38] multiblock, [39][40][41] star 42 and graft copolymers, [43][44][45] blends, 35,46 and gels 47,48 has resulted in remarkably simple thermal control over the polymer structure and related properties.…”

Olefin metathesis and quadruple hydrogen bonding: A powerful combination in multistep supramolecular synthesis

“…Such a material requires immiscible polymeric components, in which macrophase separation is prevented by strong and complementary noncovalent bonds between the telechelic blocks. Telechelic polymers with multiple H-bonding endgroups have been prepared by means of postpolymerization modification routes (14)(15)(16)(17)(18)(19)(20)(21)(22). However, incomplete reaction leads to small, yet detrimental, amounts of monofunctionalized polymers, which act as chain stoppers.…”