Synthesis and Characterization of Star-Shaped Poly(ethylene-co-propylene) Polymers Bearing Terminal Self-Complementary Multiple Hydrogen-Bonding Sites

Abstract

The polymerization of isoprene was initiated with 3-(tert-butyldimethylsilyloxy)-1-propyllithium (TBDMSPrLi), which contained a silyl-protected hydroxyl functionality. Living poly(isoprenyllithium) with controlled molecular weight and narrow molecular weight distribution coupled efficiently with divinylbenzene to form well-defined star-shaped polymers. Both linear and star-shaped polymers were subsequently hydrogenated to poly(ethylene-co-propylene) and deprotected quantitatively to yield terminal primary hydroxyl functionality. High conversions of hydroxyl functionality to the 2-ureido-4[1H]-pyrimidinone (UPy) quadruple hydrogen-bonding group were achieved using isocyanate coupling and subsequent reaction with 6-methylisocytosine. Nonfunctionalized and UPy-functionalized linear and star-shaped poly(ethylene-co-propylene)s were characterized using 1H NMR spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), tensile testing, and melt rheology. The observed glass transition temperatures were independent of molecular architecture for the UPy-functionalized polymers and nonfunctionalized analogues using both DSC and DMA. Tensile testing revealed the UPy-functionalized star polymers (UPy-Star) exhibited a higher Young's modulus and lower percent elongation at failure compared to the UPy-telechelic polymers with M n of 24 000 g/mol (UPy-24K-T) analogues. UPy-Star polymer exhibited a rubbery plateau region over a well-defined frequency range, and in contrast, the UPy-functionalized linear polymers were in the terminal flow regime, which suggested greater association for the star-shaped polymers. In addition, complex viscosity data revealed a non-Newtonian behavior for the star-shaped polymers in contrast to linear analogues, which is also consistent with a highly associated structure.

Viscoelastic signature of physisorbed macromolecules at the solid–liquid interface

“…The results indicate that an effective semidilute concentration in the boundary layers with PEG molecular weight higher than several thousand g/mol rises above that of the bulk solutions. We found that the magnitude of the reductions in gyration radius, physical parameters of these PEG molecules or the rise in local concentration of PEGs at the Au/liquid interface is consistent with those documented in the literatures [36,[66][67][68][69][70][71].…”

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.…”

“…Also, poly(ethylene-co-propylene) prepolymers were coupled to UPy-units. 79 Next to monofunctional PE-co-PP 7i, bifunctional polymers 6k and 6l and even a star-shaped structure 8e were synthesized. Trifunctional UPy-PEO-PPO copolymer 8a has been shown to assemble into supramolecular networks.…”

Pseudo‐Living Anionic Telomerization of Buta‐1,3‐diene

“…In addition, a heat-exchange coil, a thermocouple, a septum sealed port, various stainless steel transfer lines to introduce solvent (cyclohexane), and inlet/vent for purified nitrogen were equipped to the anionic reactor. [27,28] The anionic reactor system was maintained at a constant nitrogen pressure (40 psi). The 600 mL-capacity anionic polymerization reactor was filled with cyclohexane (300 mL).…”