Six perfectly regioregular polyethylene (PE)-based ionomers containing 1-methylimidazolium bromide groups on exactly every 9th, 15th, or 21st carbon (precision ionomers) and two regiorandom analogues have been synthesized and characterized via dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Because these materials were synthesized by a postpolymerization functionalization route, their number-average molecular weights (M n s) and polydispersity indices (PDIs) could be accurately calculated based on measurements of the preionized polymers; M n s range from 36 to 53 kDa with PDIs all close to 2. Thermal gravimetric analysis (TGA) indicates stability up 250°C, and DSC measurements indicate that crystallinity is a function of the polymer backbone spacer length. T m s range from ∼80 to 106°C, with longer spacer lengths inducing semicrystallinity. DSC measured glass transition temperatures (T g s) range from −1.6 to 26.8°C and appear to be dependent on both spacer length and crystallinity. DMA data loosely mirror the DSC results, but with transitions occurring at lower temperatures that we attribute to differences in the thermal history and/or the different heating ramp rates used. ■ INTRODUCTIONIonomers comprise a class of polymers containing a relatively low concentration of pendant ionic groups. At a global production rate of about 300 million pounds/year, they are of great commercial importance and find use in a range of applications as ion transport membranes, electromechanical devices, thermoplastic elastomers, adhesives, and other uses. 1 Moreover, while polyanions are by far the more common derivatives, recently there has been considerable interest in polycations, which are the focus of this paper, due to their potential applicability in anion exchange membrane fuel cells 2 and mechanical actuators. 3 Ionic polymers are often prepared via polymerization of acryloyl-or vinyl-functionalized ionic liquids or by ionization of electrically neutral polymers. 1−17 Countless studies have been and continue to be conducted in efforts to understand and control ionomer morphology. With some exceptions, such as regularly sequenced polyurethane, 18−20 polysiloxane, 21,22 and poly(ethylene oxide) 23,24 based ionomers, most current synthetic approaches yield a random (or pseudorandom) distribution of ionic groups along a polymer backbone (type A of Figure 1); thus, the impact of perfect regioregularity on ionomer morphology and performance in various applications remains largely unexplored due to a lack of synthetic methodology. 1,25 We recently reported the synthesis of an ionomer and an ionene (in which the ionic group is in the main chain of the polymer) by acyclic diene metathesis polymerization (ADMET) of α,ω-diene-functionalized ionic liquids. 26 This method, for the first time, provided access to a polyolefin-based precision ionomer (type B of Figure 1); an imidazolium hexafluorophosphate group was located on each and every 21st carbon along a linear polyolefin backbone. Synthesis of these ...

Background and aims  Benign gastrointestinal (GI) strictures are often refractory to standard endoscopic interventions. Fully covered coaxial lumen-apposing metal stents (LAMS) have emerged as a novel therapy for these strictures. The aim of this study was to evaluate the safety and efficacy of LAMS for refractory GI strictures. Patients and methods  A retrospective analysis was performed for patients who underwent LAMS placement for benign luminal strictures in three US centers between January 2014 and December 2016. The primary outcomes were technical success and initial clinical success of LAMS placement. Secondary outcomes were stent migration, rate of re-intervention, and adverse events. Results  A total of 49 patients underwent 56 LAMS placement procedures. Previous treatment had failed in 39 patients (79.6 %), and anastomotic strictures were the indication in 77.6 % (38/49), with the most common site being gastrojejunal (34.7 % [17/49]). Technical success was achieved in all procedures and initial clinical success was achieved in 96.4 % of all procedures (54/56). Patient initial clinical success was 95.9 % (47/49). Stent migration occurred in 17.9 % of procedures, and was more likely to occur at sites in the lower GI tract ( P  = 0.02). The mean stent dwell time was 100.6 days, and the mean follow-up was 169.8 days. Minor adverse events, not requiring hospitalization, occurred in 33.9 % of procedures, including subsequent stricture progression (10.7 %). In cases where LAMS were removed, mean follow-up time was 102.2 days. The re-intervention rate was 75 % at 300 days follow-up after stent removal. Of the LAMS placed at anastomotic strictures, 36.4 % required re-intervention, with approximately two-thirds of these re-interventions requiring placement of a new stent or surgery. Conclusion  LAMS placement was successful for the management of refractory GI strictures, with good technical and initial clinical success rates. However, re-intervention rates after LAMS removal were high, and many strictures were not resolved by an extended period of stenting with these coaxial stents. LAMS placement offers additional therapeutic options and in selected cases might be considered a destination therapy for patients with recalcitrant benign strictures.

Background Despite a strong link between Helicobacter Pylori infection and peptic ulcer disease (PUD), rates of testing for H. Pylori in hospitalized patients with PUD remain largely unexplored. We aimed to determine H. Pylori testing practices at our institution among inpatients with PUD, and to implement a protocol to improve testing rates. Materials and Methods In this quality improvement initiative, baseline H. Pylori testing practices were determined by analysis of historical data on 100 subsequent inpatients with PUD from January 2016 to June 2017 at a tertiary care hospital undergoing esophagogastroduodenoscopy (EGD). Subsequently, a division‐wide testing protocol was implemented, and data were analyzed from 43 consecutive inpatients with PUD from October 2019‐March 2020 to determine the protocol's effects. Results The analysis of baseline testing practices showed a 57% testing rate for H. Pylori. Gastric biopsies were less likely to be performed during EGDs done outside the endoscopy unit (5.9% vs 32.7%, P = 0.001), outside of usual business hours (6.7% vs 24.3%, P = 0.04), and in cases where endoscopic therapy was administered (6% vs 32%, P = 0.02). After implementation of the new division‐wide testing protocol, testing rates increased to 93% (P < 0.001). Conclusions Low baseline inpatient testing for H. Pylori represents a missed opportunity to test a substantial number of high‐risk patients with PUD. Implementation of a conceptually simple protocol aimed at increasing rates of gastric biopsy significantly improved testing rates in a prospective follow‐up. Widespread standardization of H. Pylori testing for inpatients with PUD may improve important patient outcomes related to complicated PUD.

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