Saccharides, based on their wide bioavailability, high chemical functionality and stereochemical diversity, are attractive starting materials for the development of new synthetic polymers. Established carbonylation methodologies were used to synthesize a 5-membered cyclic carbonate monomer, 4,6-O-benzylidene-2,3-O-carbonyl-α-d-glucopyranoside (MBGC), in high yield (>95%) from a commercially available d-glucopyranoside derivative. The ability of this monomer to undergo ring-opening polymerization (ROP) with a range of organocatalysts, rather than the previously reported anionic initiators, was investigated. These new conditions were developed to widen the functional group tolerance in the polymerization, and achieve better control over the final properties of the polymers. The most promising of the catalysts examined, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), was used in a kinetic study to confirm the well-controlled nature of the ROP. Optimized conditions were then successfully applied to the synthesis of polymers of different molecular weights. Two post-polymerization modifications were completed via the removal of the benzylidene acetal protecting group to release a water-soluble poly(glucose carbonate), and then addition of acetyl groups to facilitate characterization studies. MALDI-TOF MS analysis was performed to further probe the chemistry of the polymerization and deprotection. A wide range of thermal decomposition temperatures (233–347 °C), glass transition temperatures (87–233 °C), and water contact angles (38–128°) was achieved by this series of polymers. The hydrolytic degradability of these polymers was also examined, demonstrating differing degradation mechanisms based on the acidic vs. basic conditions used. Consequently, this single monomer was successfully employed in the straightforward synthesis of a polymeric system with tunable properties based on the molecular weight and repeat unit composition.
Aqueous ring-opening metathesis polymerization (ROMP) is a powerful tool for polymer synthesis under environmentally friendly conditions, functionalization of biomacromolecules, and preparation of polymeric nanoparticles via ROMP-induced self-assembly (ROMPISA). Although new water-soluble Ru-based metathesis catalysts have been developed and evaluated for their efficiency in mediating cross metathesis (CM) and ring-closing metathesis (RCM) reactions, little is known with regards to their catalytic activity and stability during aqueous ROMP. Here, we investigate the influence of solution pH, the presence of salt additives, and catalyst loading on ROMP monomer conversion and catalyst lifetime. We find that ROMP in aqueous media is particularly sensitive to chloride ion concentration and propose that this sensitivity originates from chloride ligand displacement by hydroxide or H 2 O at the Ru center, which reversibly generates an unstable and metathesis inactive complex. The formation of this Ru-(OH) n complex not only reduces monomer conversion and catalyst lifetime but also influences polymer microstructure. However, we find that the addition of chloride salts dramatically improves ROMP conversion and control. By carrying out aqueous ROMP in the presence of various chloride sources such as NaCl, KCl, or tetrabutylammonium chloride, we show that diblock copolymers can be readily synthesized via ROMPISA in solutions with high concentrations of neutral H 2 O (i.e., 90 v/v%) and relatively low concentrations of catalyst (i.e., 1 mol %). The capability to conduct aqueous ROMP at neutral pH is anticipated to enable new research avenues, particularly for applications in biological media, where the unique characteristics of ROMP provide distinct advantages over other polymerization strategies.
Polysulfamides are the −SO 2 − analogues of polyureas and form an intriguing family of polymers containing hydrogen-bond donor and acceptor groups. However, unlike polyureas, their physical properties are mostly unknown because of the scarcity of synthetic methods to access such polymers. Herein, we report an expedient synthesis of AB monomers for the synthesis of polysulfamides via Sulfur(VI) Fluoride Exchange (SuFEx) click polymerization. Upon optimization of the step-growth process, a variety of polysulfamides were isolated and characterized. The versatility of the SuFEx polymerization allowed structural modulation of the main chain through the incorporation of aliphatic or aromatic amines. While all synthesized polymers presented high thermal stability via thermogravimetric analysis, the glasstransition temperature and crystallinity were shown to be highly tied to the structure of the backbone between repeating sulfamide units through differential scanning calorimetry and powder X-ray diffraction. Careful analysis via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and X-ray crystallography also revealed the formation of macrocyclic oligomers during the polymerization of one AB monomer. Finally, two protocols were developed to efficiently degrade all synthesized polysulfamides through either chemical recycling for polymers derived from aromatic amines or oxidative upcycling for those based on aliphatic amines.
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