Synthesis of High Molecular Weight Polymers by Organocatalyzed Living Radical Polymerization and Self-Assembly Behavior.

A mild organocatalyzed living radical polymerization method is studied for high molecular weight polymers (HMWPs), yielding low-dispersity linear and star polymers (D = Mw /Mn = 1.03-1.28) up to Mn = 3.9 × 105 and monomer conversion = 80%, where Mn and Mw are the number- and weight-average molecular weights, respectively. Even at high degrees of polymerization (DPs > 2000), this technique still features excellent control over molecular weights and D values, indicating the living character. The macroinitiators prepared at DP = 2000 are subsequently used for block polymerizations at high DPs (>2000) with functional methacrylates, yielding linear A-B diblock, linear B-A-B triblock, and 3-arm star A-B diblock copolymers, suggesting the excellent block efficiency of macroinitiators synthesized at a high DP value (=2000). This mild organocatalyzed living radical polymerization technique can enhance the livingness of propagation radicals and kinetic chain length at high monomer conversions for monomers with moderate propagation rate coefficients (kp s), reduce the persistent radical effect as much as possible, and hence enable HMWPs without the presence of metal catalyst, exogenous initiator, or harsh equipment. The obtained amphiphilic block copolymers present unique microphase separation behavior, and hold great potential in advanced materials applications, for example, thermosensitive nanocarriers.

A Novel Type of Aspiration Presenting With Acute Respiratory Failure Caused by Upper Airway Obstruction Due to Diaper Pica.

We herein report an extremely rare case of acute respiratory failure due to pica of the high-molecular-weight polymers in a diaper (HMWPD). An 81-year-old woman was admitted to our hospital because of dyspnea. Several hours earlier, the facility staff saw her tearing the diaper and eating it. And several hours later, the staff found her complaining of dyspnea. Her chest computed tomography revealed airway foreign bodies. Immediately, flexible bronchoscopy was performed. The trachea and the bilateral bronchi were filled with the HMWPD. We tried to grasp the HMWPD with various common instruments, but the HMWPD could not be grasped. Finally, we performed direct bronchoscopic suction. All the HMWPD were removed successfully. The HMWPD have hygroscopic property resulting in volume expansion and the fatal consequence of upper airway obstruction. Physicians working in an emergency department should be aware of this acute respiratory failure due to diaper pica and its effective treatment.

Arm-First Synthesis of Star Polymers with Polywedge Arms Using Ring-Opening Metathesis Polymerization and Bifunctional Crosslinkers.

This work presents a two-step, one-pot process to make star polymers with polywedge arms. In a one-pot reaction, after the polywedge arms are synthesized, crosslinker species are added to the reaction, rapidly forming star polymers. Crosslinker species with different degrees of conformational freedom were designed and synthesized and their capacity to generate star polymers was evaluated. Mass conversions up to 92% and stars with up to 17 arms were synthesized with the most rigid crosslinker. The effects of arm molecular weight and molar ratio of crosslinker to arm on mass conversion and arms per star were explored further. Finally, the size-molecular weight scaling relationship for polywedges with linear and star architectures was compared, corroborating theoretical results regarding star polymers with arms much larger than their core.