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Mark C Petrie - One of the best experts on this subject based on the ideXlab platform.
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impact of an interatrial shunt device on survival and heart failure hospitalization in patients with preserved ejection fraction
Esc Heart Failure, 2019Co-Authors: David M Kaye, Finn Gustafsson, Gerd Hasenfuβ, Mark C Petrie, S Mckenzie, Filip Malek, Martijn Post, Robert N Doughty, Jeannoel Trochu, Irene LangAbstract:Aims: Impaired left ventricular diastolic function leading to elevated left atrial pressures, particularly during exertion, is a key driver of symptoms and outcomes in heart failure with preserved ejection fraction (HFpEF). Insertion of an interatrial shunt device (IASD) to reduce left atrial pressure in HFpEF has been shown to be associated with short‐term haemodynamic and symptomatic benefit. We aimed to investigate the potential effects of IASD placement on HFpEF survival and heart failure hospitalization (HFH). Methods and results: Heart failure with preserved ejection fraction patients participating in the Reduce Elevated Left Atrial Pressure in Patients with Heart Failure study (Corvia Medical) of an IASD were followed for a median duration of 739 days. The theoretical impact of IASD implantation on HFpEF mortality was investigated by comparing the observed survival of the study cohort with the survival predicted from baseline data using the Meta‐analysis Global Group in Chronic Heart Failure heart failure risk survival score. Baseline and post‐IASD implant parameters associated with HFH were also investigated. Based upon the individual baseline demographic and cardiovascular profile of the study cohort, the Meta‐analysis Global Group in Chronic Heart Failure score‐predicted mortality was 10.2/100 pt years. The observed mortality rate of the IASD‐treated cohort was 3.4/100 pt years, representing a 33% lower rate (P = 0.02). By Kaplan–Meier analysis, the observed survival in IASD patients was greater than predicted (P = 0.014). Baseline parameters were not predictive of future HFH events; however, poorer exercise tolerance and a higher workload‐corrected exercise pulmonary capillary wedge pressure at the 6 months post‐IASD study were associated with HFH. Conclusions: The current study suggests IASD implantation may be associated with a reduction in mortality in HFpEF. Large‐scale ongoing randomized studies are required to confirm the potential benefit of this therapy.
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impact of baseline hemodynamics on the effects of a transcatheter interatrial shunt device in heart failure with preserved ejection fraction
Circulation-heart Failure, 2018Co-Authors: Jeffrey D Wessler, Ted Feldman, David M Kaye, Finn Gustafsson, Gerd Hasenfuβ, Jan Komtebedde, Carolyn S P Lam, Mark C Petrie, Barry A Borlaug, Sanjiv J ShahAbstract:Background Interatrial shunt device (IASD) effects have been described in patients with heart failure and ejection fractions (EFs) ≥40%. However, baseline characteristics that correlate with greate...
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transcatheter interatrial shunt device for the treatment of heart failure with preserved ejection fraction reduce lap hf i reduce elevated left atrial pressure in patients with heart failure a phase 2 randomized sham controlled trial
Circulation, 2018Co-Authors: Ted Feldman, Mark J Ricciardi, Rami Kahwash, Sheldon E Litwin, Martin Penicka, David M Kaye, Laura Mauri, Pim Van Der Harst, Peter S Fail, Mark C PetrieAbstract:Background: In nonrandomized, open-label studies, a transcatheter interatrial shunt device (IASD, Corvia Medical) was associated with lower pulmonary capillary wedge pressure (PCWP), fewer symptoms, and greater quality of life and exercise capacity in patients with heart failure (HF) and midrange or preserved ejection fraction (EF ≥40%). We conducted the first randomized sham-controlled trial to evaluate the IASD in HF with EF ≥40%. Methods: REDUCE LAP-HF I (Reduce Elevated Left Atrial Pressure in Patients With Heart Failure) was a phase 2, randomized, parallel-group, blinded multicenter trial in patients with New York Heart Association class III or ambulatory class IV HF, EF ≥40%, exercise PCWP ≥25 mm Hg, and PCWP-right atrial pressure gradient ≥5 mm Hg. Participants were randomized (1:1) to the IASD versus a sham procedure (femoral venous access with intracardiac echocardiography but no IASD placement). The participants and investigators assessing the participants during follow-up were blinded to treatment assignment. The primary effectiveness end point was exercise PCWP at 1 month. The primary safety end point was major adverse cardiac, cerebrovascular, and renal events at 1 month. PCWP during exercise was compared between treatment groups using a mixed-effects repeated measures model analysis of covariance that included data from all available stages of exercise. Results: A total of 94 patients were enrolled, of whom 44 met inclusion/exclusion criteria and were randomized to the IASD (n=22) and control (n=22) groups. Mean age was 70±9 years, and 50% were female. At 1 month, the IASD resulted in a greater reduction in PCWP compared with sham control ( P =0.028 accounting for all stages of exercise). Peak PCWP decreased by 3.5±6.4 mm Hg in the treatment group versus 0.5±5.0 mm Hg in the control group ( P =0.14). There were no peri-procedural or 1-month major adverse cardiac, cerebrovascular, and renal events in the IASD group and 1 event (worsening renal function) in the control group ( P =1.0). Conclusions: In patients with HF and EF ≥40%, IASD treatment reduces PCWP during exercise. Whether this mechanistic effect will translate into sustained improvements in symptoms and outcomes requires further evaluation. Clinical Trial Registration: URL: https://clinicaltrials.gov. Unique identifier: NCT02600234.
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transcatheter interatrial shunt device for the treatment of heart failure with preserved ejection fraction reduce lap hf i reduce elevated left atrial pressure in patients with heart failure
Circulation, 2018Co-Authors: Ted Feldman, Mark J Ricciardi, Rami Kahwash, Sheldon E Litwin, Pim Van Der Harst, Martin Penicka, David M Kaye, Laura Mauri, Peter S Fail, Mark C PetrieAbstract:Background:In nonrandomized, open-label studies, a transcatheter interatrial shunt device (IASD, Corvia Medical) was associated with lower pulmonary capillary wedge pressure (PCWP), fewer symptoms,...
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transcatheter interatrial shunt device for the treatment of heart failure with preserved ejection fraction reduce lap hf i reduce elevated left atrial pressure in patients with heart failure a phase 2 randomized sham controlled trial
Circulation, 2017Co-Authors: Ted Feldman, Mark J Ricciardi, Rami Kahwash, Sheldon E Litwin, Pim Van Der Harst, Martin Penicka, David M Kaye, Laura Mauri, Peter S Fail, Mark C PetrieAbstract:Background —In non-randomized, open-label studies, a transcatheter interatrial shunt device (IASD, Corvia Medical) was associated with lower pulmonary capillary wedge pressure (PCWP), less symptoms, and greater quality of life and exercise capacity in patients with heart failure (HF) and mid-range or preserved ejection fraction (EF ≥ 40%). We conducted the first randomized, sham-controlled trial to evaluate the IASD in HF with EF ≥ 40%. Methods —REDUCE LAP-HF I was a phase 2, randomized, parallel-group, blinded multicenter trial in patients with New York Heart Association (NYHA) class III or ambulatory class IV HF, EF ≥ 40%, exercise PCWP ≥ 25 mmHg, and PCWP-right atrial pressure gradient ≥ 5 mmHg. Participants were randomized (1:1) to the IASD vs. a sham procedure (femoral venous access with intracardiac echocardiography but no IASD placement). The participants and investigators assessing the participants during follow-up were blinded to treatment assignment. The primary effectiveness endpoint was exercise PCWP at 1 month. The primary safety endpoint was major adverse cardiac, cerebrovascular, and renal events (MACCRE) at 1 month. PCWP during exercise was compared between treatment groups using a mixed effects repeated measures model analysis of covariance that included data from all available stages of exercise. Results —A total of 94 patients were enrolled, of which n=44 met inclusion/exclusion criteria and were randomized to the IASD (n=22) and control (n=22) groups. Mean age was 70±9 years and 50% were female. At 1 month, the IASD resulted in a greater reduction in PCWP compared to sham-control (P=0.028 accounting for all stages of exercise). Peak PCWP decreased by 3.5±6.4 mmHg in the treatment group vs. 0.5±5.0 mmHg in the control group (P=0.14). There were no peri-procedural or 1-month MACCRE in the IASD group and 1 event (worsening renal function) in the control group (P=1.0). Conclusions —In patients with HF and EF ≥ 40%, IASD treatment reduces PCWP during exercise. Whether this mechanistic effect will translate into sustained improvements in symptoms and outcomes requires further evaluation. Clinical Trial Registration —URL: http://clinicaltrials.gov. Unique identifier: NCT02600234
Ryong Ryoo - One of the best experts on this subject based on the ideXlab platform.
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adsorption and structural properties of ordered mesoporous carbons synthesized by using various carbon precursors and ordered siliceous p6mm and Ia3d mesostructures as templates
Journal of Physical Chemistry B, 2005Co-Authors: Kamil P Gierszal, Ryong Ryoo, Mietek JaroniecAbstract:Adsorption and structural properties of inverse carbon replicas of two ordered siliceous P6mm and Ia3d mesostructures have been studied by nitrogen adsorption, powder X-ray diffraction, and transmission electron microscopy. These carbon replicas were prepared by filling the pores of SBA-15 and KIT-6 siliceous templates with various carbon precursors followed by carbonization and silica dissolution. Sucrose, furfuryl alcohol, acenaphthene, mesophase pitch, and petroleum pitch were used to obtain inverse carbon replicas of SBA-15 and KIT-6. While structural properties of the resulting ordered mesoporous carbons are mainly determined by the hard template used, their adsorption properties depend on the type of the carbon precursor.
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mcm 48 like large mesoporous silicas with tailored pore structure facile synthesis domain in a ternary triblock copolymer butanol water system
Journal of the American Chemical Society, 2005Co-Authors: Freddy Kleitz, Blain Paul, Ryong RyooAbstract:Assembly of mesostructured silica using Pluronic P123 triblock copolymer (EO20−PO70−EO20) and n-butanol mixture is a facile synthesis route to the MCM-48-like ordered large mesoporous silicas with the cubic Ia3d mesostructure. The cubic phase domain is remarkably extended by controlling the amounts of butanol and silica source correspondingly. The extended phase domain allows synthesis of the mesoporous silicas with various structural characteristics. Characterization by powder X-ray diffraction, nitrogen physisorption, scanning electron microscopy, and transmission electron microscopy reveals that the cubic Ia3d materials possess high specific surface areas, high pore volumes, and readily tunable pore diameters in narrow distribution of sizes ranging from 4 to 12 nm. Moreover, generation of complementary pores between the two chiral channels in the gyroid Ia3d structure can be controlled systematically depending on synthesis conditions. Carbon replicas, using sucrose as the carbon precursor, are obtai...
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synthesis of thermally stable mesoporous cerium oxide with nanocrystalline frameworks using mesoporous silica templates
Chemical Communications, 2003Co-Authors: S C Laha, Ryong RyooAbstract:Highly ordered mesoporous cerium oxides, composed of nanocrystalline pore walls and exhibiting high thermal stability even at 973 K, were synthesized using mesoporous silica templates with hexagonal p6mm and cubic Ia3d symmetries.
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cubic Ia3d large mesoporous silica synthesis and replication to platinum nanowires carbon nanorods and carbon nanotubes
Chemical Communications, 2003Co-Authors: Freddy Kleitz, Shin Hei Choi, Ryong RyooAbstract:A new synthesis route to high-quality large mesoporous cubic Ia3d silica is reported, utilizing a triblock copolymer (EO20PO70EO20)–butanol mixture for the structure direction in aqueous solution.
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generalised route to the preparation of mesoporous metallosilicates via post synthetic metal implantation
Chemical Communications, 1997Co-Authors: Ryong Ryoo, Mi Jeong KimAbstract:A post-synthesis route, through which various metal elements can be grafted onto siliceous frameworks using non-aqueous solutions of AlCl3, Al(NO3)3, SnCl2, Zn(O2CMe)2 Mn(O2CMe)2, etc., is developed as a generalised means to obtain mesoporous metallosilicates molecular sieves with various structures such as MCM-41 (hexagonal), MCM-48 (cubic Ia3d), SBA-1 (cubic Pm3n), KIT-1 (disordered) and MSU-1 (disordered) with superior structural integrity, acidity and catalytic activity to those of materials having metals incorporated during synthesis.
Ted Feldman - One of the best experts on this subject based on the ideXlab platform.
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transcatheter interatrial shunt device for the treatment of heart failure rationale and design of the pivotal randomized trial to reduce elevated left atrial pressure in patients with heart failure ii reduce lap hf ii
American Heart Journal, 2020Co-Authors: Natalia Berry, Ted Feldman, Jan Komtebedde, Joseph M Massaro, Laura Mauri, Dirk J Van Veldhuisen, Scott D Solomon, Sanjiv J ShahAbstract:Background A randomized, sham-controlled trial in patients with heart failure (HF) and left ventricular ejection fraction (LVEF) ≥40% demonstrated reductions in pulmonary capillary wedge pressure (PCWP) with a novel transcatheter InterAtrial Shunt Device (IASD). Whether this hemodynamic effect will translate to an improvement in cardiovascular outcomes and symptoms requires additional study. Study design and objectives REDUCE Elevated Left Atrial Pressure in Patients with Heart Failure II (REDUCE LAP HF-II) is a multicenter, prospective, randomized, sham-controlled, blinded trial designed to evaluate the clinical efficacy of the IASD in symptomatic HF and elevated left atrial pressures. Up to 608 HF patients age ≥ 40 years with LVEF ≥40%, PCWP ≥25 mm Hg during supine ergometer exercise, and PCWP ≥5 mm Hg higher than right atrial pressure will be randomized 1:1 to the IASD versus sham control. Key exclusion criteria include hemodynamically significant valvular disease, evidence of pulmonary arterial hypertension, and right heart dysfunction. The primary endpoint is a hierarchical composite, analyzed by the Finkelstein-Schoenfeld methodology, that includes (1) cardiovascular mortality or first nonfatal ischemic stroke through 12 months; (2) total (first plus recurrent) HF hospitalizations or healthcare facility visits for intravenous diuretics up to 24 months, analyzed when the last randomized patient completes 12 months of follow-up; and (3) change in Kansas City Cardiomyopathy Questionnaire overall summary score from baseline to 12 months. Follow-up echocardiography will be performed at 6, 12, and 24 months to evaluate shunt flow and cardiac chamber size/function. Patients will be followed for a total of 5 years after the index procedure. Conclusions REDUCE LAP-HF II is designed to evaluate the clinical efficacy of the IASD device in patients with symptomatic HF with elevated left atrial pressure and LVEF ≥40%.
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one year safety and clinical outcomes of a transcatheter interatrial shunt device for the treatment of heart failure with preserved ejection fraction in the reduce elevated left atrial pressure in patients with heart failure reduce lap hf i trial a r
JAMA Cardiology, 2018Co-Authors: Sanjiv J Shah, Ted Feldman, Mark J Ricciardi, Rami Kahwash, Scott Lilly, Sheldon E Litwin, Christopher D Nielsen, Pim Van Der Harst, Elke S Hoendermis, Martin PenickaAbstract:Importance In patients with heart failure (HF) and left ventricular ejection fraction (LVEF) equal to or greater than 40%, a transcatheter interatrial shunt device (IASD; Corvia Medical) reduces exercise pulmonary capillary wedge pressure (PCWP) and is safe compared with sham control treatment at 1 month of follow-up. The longer-term safety and patency of the IASD has not yet been demonstrated in the setting of a randomized clinical trial (RCT). Objective: To evaluate the 1-year safety and clinical outcomes of the IASD compared with a sham control treatment. Design, Setting, and Participants: This phase 2, double-blind, 1-to-1 sham-controlled multicenter RCT of IASD implantation vs a sham procedure (femoral venous access and imaging of the interatrial septum without IASD) was conducted in 22 centers in the United States, Europe, and Australia on patients with New York Heart Association (NYHA) class III or ambulatory class IV HF, LVEF equal to or greater than 40%, exercise PCWP equal to or greater than 25 mm Hg, and PCWP-right atrial pressure gradient equal to or greater than 5 mm Hg. Main Outcomes and Measures: Safety was assessed by major adverse cardiac, cerebrovascular, or renal events (MACCRE). Exploratory outcomes evaluated at 1 year were hospitalizations for HF, NYHA class, quality of life, a 6-minute walk test, and device patency. Results: After 1 year, shunts were patent in all IASD-treated patients; MACCRE did not differ significantly in the IASD arm (2 of 21 [9.5%]) vs the control arm (5 of 22 [22.7%]; P = .41), and no strokes occurred. The yearly rate of hospitalizations for HF was 0.22 in the IASD arm and 0.63 in the control arm (P = .06). Median improvement in NYHA class was 1 class in the IASD arm (IQR, −1 to 0) vs 0 in the control arm (IQR, −1 to 0; P = .08). Quality of life and 6-minute walk test distance were similar in both groups. At 6 months, there was an increase in right ventricular size in the IASD arm (mean [SD], 7.9 [8.0] mL/m2) vs the control arm (−1.8 [9.6] mL/m2; P = .002), consistent with left-to-right shunting through the device; no further increase occurred in the IASD arm at 12 months. Conclusions and Relevance: The REDUCE LAP-HF I phase 2, sham-controlled RCT confirms the longer-term patency of the IASD. Through 1 year of follow-up, IASD treatment appears safe, with no significant differences in MACCRE in patients receiving IASD compared with those who received sham control treatment. Trial Registration: ClinicalTrials.gov identifier: NCT02600234
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impact of baseline hemodynamics on the effects of a transcatheter interatrial shunt device in heart failure with preserved ejection fraction
Circulation-heart Failure, 2018Co-Authors: Jeffrey D Wessler, Ted Feldman, David M Kaye, Finn Gustafsson, Gerd Hasenfuβ, Jan Komtebedde, Carolyn S P Lam, Mark C Petrie, Barry A Borlaug, Sanjiv J ShahAbstract:Background Interatrial shunt device (IASD) effects have been described in patients with heart failure and ejection fractions (EFs) ≥40%. However, baseline characteristics that correlate with greate...
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transcatheter interatrial shunt device for the treatment of heart failure with preserved ejection fraction reduce lap hf i reduce elevated left atrial pressure in patients with heart failure a phase 2 randomized sham controlled trial
Circulation, 2018Co-Authors: Ted Feldman, Mark J Ricciardi, Rami Kahwash, Sheldon E Litwin, Martin Penicka, David M Kaye, Laura Mauri, Pim Van Der Harst, Peter S Fail, Mark C PetrieAbstract:Background: In nonrandomized, open-label studies, a transcatheter interatrial shunt device (IASD, Corvia Medical) was associated with lower pulmonary capillary wedge pressure (PCWP), fewer symptoms, and greater quality of life and exercise capacity in patients with heart failure (HF) and midrange or preserved ejection fraction (EF ≥40%). We conducted the first randomized sham-controlled trial to evaluate the IASD in HF with EF ≥40%. Methods: REDUCE LAP-HF I (Reduce Elevated Left Atrial Pressure in Patients With Heart Failure) was a phase 2, randomized, parallel-group, blinded multicenter trial in patients with New York Heart Association class III or ambulatory class IV HF, EF ≥40%, exercise PCWP ≥25 mm Hg, and PCWP-right atrial pressure gradient ≥5 mm Hg. Participants were randomized (1:1) to the IASD versus a sham procedure (femoral venous access with intracardiac echocardiography but no IASD placement). The participants and investigators assessing the participants during follow-up were blinded to treatment assignment. The primary effectiveness end point was exercise PCWP at 1 month. The primary safety end point was major adverse cardiac, cerebrovascular, and renal events at 1 month. PCWP during exercise was compared between treatment groups using a mixed-effects repeated measures model analysis of covariance that included data from all available stages of exercise. Results: A total of 94 patients were enrolled, of whom 44 met inclusion/exclusion criteria and were randomized to the IASD (n=22) and control (n=22) groups. Mean age was 70±9 years, and 50% were female. At 1 month, the IASD resulted in a greater reduction in PCWP compared with sham control ( P =0.028 accounting for all stages of exercise). Peak PCWP decreased by 3.5±6.4 mm Hg in the treatment group versus 0.5±5.0 mm Hg in the control group ( P =0.14). There were no peri-procedural or 1-month major adverse cardiac, cerebrovascular, and renal events in the IASD group and 1 event (worsening renal function) in the control group ( P =1.0). Conclusions: In patients with HF and EF ≥40%, IASD treatment reduces PCWP during exercise. Whether this mechanistic effect will translate into sustained improvements in symptoms and outcomes requires further evaluation. Clinical Trial Registration: URL: https://clinicaltrials.gov. Unique identifier: NCT02600234.
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transcatheter interatrial shunt device for the treatment of heart failure with preserved ejection fraction reduce lap hf i reduce elevated left atrial pressure in patients with heart failure
Circulation, 2018Co-Authors: Ted Feldman, Mark J Ricciardi, Rami Kahwash, Sheldon E Litwin, Pim Van Der Harst, Martin Penicka, David M Kaye, Laura Mauri, Peter S Fail, Mark C PetrieAbstract:Background:In nonrandomized, open-label studies, a transcatheter interatrial shunt device (IASD, Corvia Medical) was associated with lower pulmonary capillary wedge pressure (PCWP), fewer symptoms,...
Frank S Bates - One of the best experts on this subject based on the ideXlab platform.
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core shell gyroid morphology in a poly isoprene block styrene block dimethylsiloxane triblock copolymer
Journal of the American Chemical Society, 1999Co-Authors: Terri Shefelbine, Damian Hajduk, Martin Etchells Vigild, M W Matsen, Marc A Hillmyer, Edward L Cussler, Frank S BatesAbstract:We report a new morphology in a poly(isoprene-block-styrene-block-dimethylsiloxane) ABC triblock copolymer. The most probable symmetry of the morphology (Ia3d) was determined from two-dimensional SAXS measurements performed on a sample with long-range order induced by an oscillatory shear field. By comparing the predictions of self-consistent field theory with TEM and SAXS and SANS powder diffraction patterns, we deduced that the morphology is a core−shell gyroid comprised of two independent and triply periodic poly(dimethylsiloxane) networks encased in poly(styrene) shells and separated by a continuous poly(isoprene) domain. Thus, this unique nanostructure divides space into five independent, three-dimensionally continuous domains.
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order disorder and composition fluctuation effects in low molar mass hydrocarbon poly dimethylsiloxane diblock copolymers
Macromolecules, 1996Co-Authors: Kristoffer Almdal, Anthony J Ryan, Kell Mortensen, Frank S BatesAbstract:Four block copolymer meltstwo poly(isoprene-block-dimethylsiloxane) (PI−PDMS) and two poly(ethylene-alt-propylene-block-dimethylsiloxane) (PEP−PDMS)have been investigated through rheological measurements, SANS, and SAXS. In both systems, lamellar to disorder and Ia3d bicontinuous to disorder transitions have been observed. Upon heating, the sequence of phases lamellae, modified layers, bicontinuous Ia3d, disorder is observed in the f = 0.65 PEP−PDMS sample. Composition fluctuations dominate the disordered state properties over an unprecedented wide temperature window in the f = 0.49 PEP−PDMS sample. The fluctuations are evident both in SANS measurements and through the temperature dependence of the viscosity. The phase behavior of these relatively low molar mass block copolymer melts, which range from 6 to 10 kg/mol, is qualitatively anticipated by the trends reported earlier for progressively lower molar mass diblock copolymers.
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polyisoprene polystyrene diblock copolymer phase diagram near the order disorder transition
Macromolecules, 1995Co-Authors: Frank S Bates, Stephan Forster, Ashish K Khandpur, Ian W Hamley, Anthony J Ryan, Wim Bras, Kristoffer Almdal, Kell MortensenAbstract:The phase behavior of ten polyisoprene-polystyrene (PI-PS) diblock copolymers, spanning the composition range from 0.24 to 0.82 polyisoprene volume fraction (f PI ), has been studied near the order-disorder transition (ODT). Dynamic mechanical spectroscopy, transmission electron microscopy, and neutron and X-ray scattering have been used to characterize phase transition temperatures and ordered state symmetries. Five distinct microstructures were observed for this chemical system : spheres, hexagonally packed cylinders (HEX), lamellae (LAM), hexagonally perforated layers (HPL), and a bicontinuous cubic phase having an Ia3d space group symmetry. The bicontinuous Ia3d phase only occurs in the vicinity of the ODT between the HEX and LAM states at compositions of 0.65 ≤ f pI ≤ 0.68 and 0.36 ≤ f pI ≤ 0.39 (prior report). Farther from the ODT, within these composition ranges, the HPL phase occurs. We did not find the ordered bicontinuous double diamond (OBDD) morphology at any composition or temperature studied, and the overall phase diagram is qualitatively different from those reported previously for PI-PS block copolymers.
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complex phase behavior of polyisoprene polystyrene diblock copolymers near the order disorder transition
Macromolecules, 1994Co-Authors: Stephan Forster, Frank S Bates, Ashish K Khandpur, Jin Zhao, Ian W Hamley, Anthony J Ryan, Wim BrasAbstract:The phase behavior of polyisoprene-polystyrene (PI-PS) diblock copolymers near the order disorder transition was investigated using dynamic mechanical measurements, TEM, SAXS and SANS at polyisoprene volume fractions 0.33< F PI < 0.42. Two new ordered morphologies have been documented between hexagonally packed cylinders (HEX) and lamellae (LAM). At low temperatures a hexagonally perforated layered (HPL) microstructure occurs, that transforms into a bicontinuous cubic phase characterized by Ia3d space group symmetry near the order disorder transition (ODT). The ordered-bicontinuous double diamind (OBDD) phase was not found at any temperature or composition studied
Ashish K Khandpur - One of the best experts on this subject based on the ideXlab platform.
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polyisoprene polystyrene diblock copolymer phase diagram near the order disorder transition
Macromolecules, 1995Co-Authors: Frank S Bates, Stephan Forster, Ashish K Khandpur, Ian W Hamley, Anthony J Ryan, Wim Bras, Kristoffer Almdal, Kell MortensenAbstract:The phase behavior of ten polyisoprene-polystyrene (PI-PS) diblock copolymers, spanning the composition range from 0.24 to 0.82 polyisoprene volume fraction (f PI ), has been studied near the order-disorder transition (ODT). Dynamic mechanical spectroscopy, transmission electron microscopy, and neutron and X-ray scattering have been used to characterize phase transition temperatures and ordered state symmetries. Five distinct microstructures were observed for this chemical system : spheres, hexagonally packed cylinders (HEX), lamellae (LAM), hexagonally perforated layers (HPL), and a bicontinuous cubic phase having an Ia3d space group symmetry. The bicontinuous Ia3d phase only occurs in the vicinity of the ODT between the HEX and LAM states at compositions of 0.65 ≤ f pI ≤ 0.68 and 0.36 ≤ f pI ≤ 0.39 (prior report). Farther from the ODT, within these composition ranges, the HPL phase occurs. We did not find the ordered bicontinuous double diamond (OBDD) morphology at any composition or temperature studied, and the overall phase diagram is qualitatively different from those reported previously for PI-PS block copolymers.
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complex phase behavior of polyisoprene polystyrene diblock copolymers near the order disorder transition
Macromolecules, 1994Co-Authors: Stephan Forster, Frank S Bates, Ashish K Khandpur, Jin Zhao, Ian W Hamley, Anthony J Ryan, Wim BrasAbstract:The phase behavior of polyisoprene-polystyrene (PI-PS) diblock copolymers near the order disorder transition was investigated using dynamic mechanical measurements, TEM, SAXS and SANS at polyisoprene volume fractions 0.33< F PI < 0.42. Two new ordered morphologies have been documented between hexagonally packed cylinders (HEX) and lamellae (LAM). At low temperatures a hexagonally perforated layered (HPL) microstructure occurs, that transforms into a bicontinuous cubic phase characterized by Ia3d space group symmetry near the order disorder transition (ODT). The ordered-bicontinuous double diamind (OBDD) phase was not found at any temperature or composition studied