Block Junction Research Articles

A novel structure of less switching loss IGBT with super junction

In order to further reduce the switching loss (ESW), a novel floating CS layer and super-junction insulated gate bipolar transistor (FCS-SJBJ-IGBT) with internal barrier junction is proposed and simulated. On the premise of not affecting breakdown voltage (BV), the CS layer of FCS-SJBJ-IGBT is floating, so that the P-body is connected with the P-drift region, and a small part of P-pillar is formed between the CS layer and the left gate, which enables electrons to flow rapidly through this region in the on state, and provides an extraction hole path in the off state to reduce the loss. The simulation results show that，under the same forward conduction voltage (VON) condition, the turn-on energy loss (EON) of FCS-SJBJ-IGBT is significantly lower than that of the traditional super-junction IGBT (con-SJ-IGBT) and 34.5 % lower than that of the recently reported super-junction IGBT (SJBJ-IGBT) with blocking junction, P-pillar and N-pillar, while their turn-off energy loss (EOFF) is almost the same. The research results can provide important reference for reducing the ESW of IGBT.

Si-Containing Reverse-Gradient Block Copolymer for Inorganic Pattern Amplification in EUV Lithography.

Although extreme ultraviolet lithography (EUVL) has emerged as a leading technology for achieving high quality sub-10 nm patterns, the insufficient pattern height of photoresist patterns remains a challenge. Directed self-assembly (DSA) of block copolymers (BCPs) is expected to be a complementary technology for EUVL due to its ability to form periodic nanostructures. However, for a combination with EUV patterns, it is essential to develop advanced BCP systems that are suited to inorganic-containing EUV photoresists and offer improved resolution limits, pattern quality, and etch resistance. Here, we report a reverse-gradient BCP system, poly[(styrene-gradient-pentafluorostyrene)-b-4-tert-butyldimetilsiloxystyrene] [P(S-g-PFS)-b-P4BDSS] BCP, which enables universally vertically oriented lamellae even in the absence of a neutral layer, while also containing a Si-containing block with high etch resistance. The gradient block, characterized by a gradual compositional transition from the block junction to the tail, plays a crucial role in creating an adequate surface energy contrast that energetically drives the formation of perpendicular lamellae without neutral layer. When used as a pattern height enhancement layer in EUVL, a high aspect ratio (3.29) of patterns was achieved, thereby offering a supplementary solution for next-generation EUVL.

Bottlebrush Block Copolymers at the Interface of Immiscible Liquids: Adsorption and Lateral Packing.

Amphiphilic bottlebrush block copolymers (BBCPs), having a hydrophilic bottlebrush polymer (BP) linked covalently to a hydrophobic BP, were found to segregate to liquid-liquid interfaces to minimize the free energy of the system. The key parameter influencing the outcome of the experiments is the ratio between the degree of polymerization of the backbone (NBB) and that of the side-chain brushes (NSC). Specifically, a spherical, star-like configuration results when NBB < NSC, while a cylindrical, bottlebrush-like shape is preferred when NBB > NSC. Dynamic interfacial tension (γ) and fluorescence recovery after photobleaching (FRAP) measurements show that the BBCP configuration influences the areal density and in-plane diffusion at the fluid interface. The characteristic relaxation times associated with BBCP adsorption (τA) and reorganization (τR) were determined by fitting time-dependent interfacial tension measurements to a sum of two exponential relaxation functions. Both τA and τR initially increased with NBB up to 92 repeat units, due to the larger hydrodynamic radius in solution and slower in-plane diffusivity, attributed to a shorter cross-sectional diameter of the side-chains near the block junction. This trend reversed at NBB = 190, with shorter τA and τR attributed to increased segregation strength and exposure of the bare water/toluene interface due to tilting and/or wiggling of the backbone chains, respectively. The adsorption energy barrier decreased with higher NBB, due to a reduced BBCP packing density at the fluid interface. This study provides fundamental insights into macromolecular assembly at fluid interfaces, as it pertains to unique bottlebrush block architectures.

A Float P-Drift and Blocking Junction LIGBT With Low Turn-Off Loss and No-Snapback

A Float P-Drift and Blocking Junction LIGBT With Low Turn-Off Loss and No-Snapback

Thermodynamics and morphology of linear multiblock copolymers at homopolymer interfaces.

Block copolymers at homopolymer interfaces are poised to play a critical role in the compatibilization of mixed plastic waste, an area of growing importance as the rate of plastic accumulation rapidly increases. Using molecular dynamics simulations of Kremer-Grest polymer chains, we have investigated how the number of blocks and block degree of polymerization in a linear multiblock copolymer impacts the interface thermodynamics of strongly segregated homopolymer blends, which is key to effective compatibilization. The second virial coefficient reveals that interface thermodynamics are more sensitive to block degree of polymerization than to the number of blocks. Moreover, we identify a strong correlation between surface pressure (reduction of interfacial tension) and the spatial uniformity of block junctions on the interface, yielding a morphological framework for interpreting the role of compatibilizer architecture (number of blocks) and block degree of polymerization. These results imply that, especially at high interfacial loading, the choice of architecture of a linear multiblock copolymer compatibilizing surfactant does not greatly affect the modification of interfacial tension.

Numerical analysis of an ultralow switching loss IGBT with super junction and blocking junction

In order to reduce the switching loss (ESW) and enhance the breakdown voltage (BV), in this paper, an insulated gate bipolar transistor with an internal blocking junction and super junction (SJBJ-IGBT) is proposed and investigated. By inserting P-pillar and N-pillar on both sides of the drift region, a drift area with auxiliary depletion function can be formed. The junction of the primary blocking layer (JPB) is located internally in the device’s drift region. The JPB is reverse biased and withstand the main E-field during device turn-off. Meanwhile, the JPB is surrounded by P-pillar and N-pillar, reducing the E-field(E-field) peak value of device, and making E-field distribution more uniform. Furthermore, during device turn-on, the reduction of the effective area of drift region makes it easier for the JPB side of the P-drift region to accumulate excess holes. So that the SJBJ-IGBT is easier to turn-on. The snapback phenomenon of SJBJ-IGBT is eliminated. Simulation results demonstrate that, under the same forward conduction voltage (VON) condition, the proposed device exhibits a significantly lower turn-on energy loss (EON) compared to the traditional super junction(SJ-IGBT), and is 44.5% lower than that of IPBJ-IGBT, while their turn-off energy losses (EOFF) are almost equivalent.Besides, the optimized E-field distribution in the SJBJ-IGBT shows 13.2% improvement of BV. Researching results can provide important reference for reducing the ESW of IGBT.

Five-axis toolpath interpolation method with kinematic corner smoothing and time synchronization

osMost toolpaths of high speed five-axis machining are composed of discrete tool positions and tool orientation vectors. Thus, toolpath smoothing is essential for increasing the machining efficiency and quality. Traditional smoothing methods face the difficulties of synchronization, computational load, feedrate fluctuation and overshoot due to the inefficient procedure of geometric smoothing followed by interpolation. To break these bottlenecks, a novel interpolation method for five-axis toolpaths with kinematic corner smoothing and time synchronization is proposed in this paper. Rather than smoothing the toolpaths geometrically, the translational velocity of tool position and the rotary angular velocity of tool orientation are directly scheduled in the workpiece coordinate system (WCS). Additionally, algorithms of time synchronization and interpolation are proposed to synchronize translation with rotation, and calculate interpolated tool positions and orientations efficiently. Simulation and experimental studies are conducted to validate the effectiveness and feasibility of the proposed method. Compared with a geometric corner smoothing method, the proposed method generates interpolated toolpaths perfectly respecting the geometric and kinematic constraints. Both the tangential and the axial kinematic profiles obtained by the proposed method are smooth and free of jitters at block junctions. Furthermore, the proposed method improves the machined surface quality, and reduces the computational time by over 50 % without solving optimization problems or scheduling recursively.

The deep structure of the Kuznetsk deflection and Kamzhelinsky block junction zone of the Kuznetsk Alatau according to magnetotelluric sounding data

The deep structure of the Kuznetsk deflection and Kamzhelinsky block junction zone of the Kuznetsk Alatau according to magnetotelluric sounding data

Single event burnout failures caused in silicon carbide power devices by alpha particles emitted from radionuclides

Single event burnouts (SEB) threaten the safe operation of high voltage SiC power devices in a wide range of applications. The triggering of this failure mechanism has been widely documented for the case of heavy ions and neutron interactions. In this study, it is demonstrated experimentally that destructive SEB events can be triggered in SiC and Si power devices by single alpha particles in the 5 MeV energy range, such as those emitted by radioactive isotopes. Such SEB events have been observed for blocking voltages lower than the breakdown voltage of the investigated devices. The experimental setup making use of an Am241 planar source to quantitatively observe the current pulses resulting from irradiation is described in detail. The mechanism of SEB initiation by single alpha particles has been investigated by the means of TCAD simulation.The experimental and simulation results show that alpha particles can trigger SEB in both SiC and Si power devices, with SiC devices exhibiting a graver susceptibility. In particular, the simulations demonstrate that the thermal runaway is a consequence of current filamentation in the main blocking junction of the devices, due to generation of a streamer along the ionization track produced by the impinging particle. Furthermore, it is shown that the increased susceptibility of SiC devices to destructive SEB is due to the stronger local field, thinner depleted region and higher junction capacitance than in Si, resulting in higher available energy for the destructive event. The present findings may have practical implications. Given the simplicity and economy of the procedure, alpha sources can be used as a complementary technique to nucleon irradiation for the characterization of the susceptibility of power devices to SEB. Finally, the possible impact on the triggering of SEBs by alpha emitters present as contamination near the active areas of the device should be reconsidered.

Synthesis and Structure‐Driven Acid‐Catalyzed Degradation of Benzoic Cyclic Acetal‐Labeled PEG Precursors toward Shell‐Sheddable PLA Block Copolymer Synthesis

AbstractThe synthesis of acid‐degradable poly(ethylene glycol) (PEG) precursors labeled with benzoic cyclic acetal (BzCA) is reported. To get an insight into their acid‐catalyzed hydrolysis, three precursors are designed with spacers exhibiting different inductive effects between PEG and BzCA linkage. The 1H‐NMR analysis confirms the order of increasing acid‐catalyzed hydrolysis to be ether &gt; ester oxygen &gt; ester carbonyl, which can be attributed to their ability to stabilize benzylic carbocation intermediates formed during hydrolysis. The formed precursors tend to be stable under a tin‐catalyzed condition for ring opening polymerization of lactide (LA), thus enabling the synthesis of well‐controlled acid‐degradable PEG‐based PLA block copolymers labeled with BzCA linkage at the block junction. When being exposed to acidic pH, the copolymers degrade through the cleavage of the junction BzCA linkages. These results guide the design principle of acid‐degradable shell‐sheddable BzCA‐bearing block copolymers for control over their acid‐catalyzed degradation and potentially drug release kinetics.

Numerical Analysis of an Ultralow Switching Loss IGBT With an Inner Primary Blocking Junction

To reduce switching loss, an insulated gate bipolar transistor (IGBT) with an inner primary blocking junction (IPBJ) is proposed and investigated. By inserting a P-drift between the N-drift and carrier storage (CS) layer, a primary blocking junction ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{\text {PB}}{)}$ </tex-math></inline-formula> of the P-drift/N-drift junction and a secondary blocking junction ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{\text {SB}}{)}$ </tex-math></inline-formula> of the P body/CS layer junction are formed. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{\text {PB}}$ </tex-math></inline-formula> is in the inner of the drift region and supports most of the blocking voltage. This reduces the electric potential in the CS layer and hole density in the hole inversion layer around the trench gate during the turn-on transient. Consequently, its turn-on loss ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {on}}{)}$ </tex-math></inline-formula> and electromagnetic interference (EMI) noise tradeoff relationship is improved. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{\text {PB}}$ </tex-math></inline-formula> is forward-biased by the ON-state excess hole in the P-drift. Thus, no electric field ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}$ </tex-math></inline-formula> -field) builds in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{\text {PB}}$ </tex-math></inline-formula> until the excess hole in the P-drift is swept out by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}$ </tex-math></inline-formula> -field extending from the reverse-biased <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{\text {SB}}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{\text {PB}}$ </tex-math></inline-formula> . Hence, with almost no excess hole in the P-drift, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}$ </tex-math></inline-formula> -field in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{\text {PB}}$ </tex-math></inline-formula> can build fast in both the P-drift and N-drift directions. This reduces the collector voltage rising time, as well as turn-off loss ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {off}}{)}$ </tex-math></inline-formula> . Simulation results show that, compared with the state-of-the-art carrier-stored trench-gate bipolar transistor (CSTBT), the proposed 650-V class silicon IPBJ-IGBT reduces <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {off}}$ </tex-math></inline-formula> by 79.7% with the same ON-state voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {on}}{)}$ </tex-math></inline-formula> and reduces <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {on}}$ </tex-math></inline-formula> by 77.9% with the same current overshoot ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {peak}}{)}$ </tex-math></inline-formula> . Besides, with its <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}$ </tex-math></inline-formula> -field and electric potential distribution optimized, the IPBJ-IGBT also improves its blocking characteristic, short-circuit withstand capability, and unclamped inductive switching performance.

Robust Through-Fin Avalanche in Vertical GaN Fin-JFET With Soft Failure Mode

We study the inherent ruggedness of the avalanche through the fin channel, a new avalanche mode in a vertical GaN power Fin-JFET, through single-pulse and repetitive avalanche circuit tests. By turning on the gate during avalanche, the major avalanche current path migrates from the p-GaN gate to the n-GaN fin channel. The single-pulse critical avalanche energy density ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {AVA}}$ </tex-math></inline-formula> ) was measured to be 10 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is the highest reported in GaN transistors. The Fin-JFET withstood over 3700 repetitive avalanche pulses at 70% of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {AVA}}$ </tex-math></inline-formula> . It exhibits a failure-to-open-circuit signature in single and repetitive avalanche. This soft failure mode allows the device to retain its full breakdown voltage, which is highly desirable for system robustness. By contrast, the through-gate avalanche in Fin-JFETs and the reported avalanche in Si and SiC transistors all show a destructive, failure-to-short-circuit signature. These results show the viability of soft avalanche failure in power devices, provide key robustness references for GaN devices, and suggest the fundamental superiority of moving the avalanche path away from the major blocking junction.

Dynamic Monte Carlo simulations of strain-induced crystallization in multiblock copolymers: effects of dilution.

Multiblock copolymers containing alternating semicrystalline and molten blocks are good thermoplastic elastomers. Their crystallization in the stretching process is however complicated by the dilution effects, prior microphase separation and contrast chain rigidity of the molten blocks. We designed our systematic investigation with three integrated steps, and herein, as the first step, we considered only the dilution effects without prior microphase separation and contrast chain rigidity. We compared two extreme situations of local dilution separately corresponding to parallel-posited and antiparallel-posited block copolymers upon strain-induced crystallization. Our dynamic Monte Carlo simulations of diblock and tetrablock copolymers demonstrated that the stretching introduces a constraint on the diffusion of locally posited crystallizable blocks along the stretching direction for crystallization and thus enhances the dilution effects to result in a higher diversity in crystal stabilities. We observed that the strain-induced crystallization of parallel-posited copolymers behaved like the melt crystallization of homopolymers; in contrast, the strain-induced crystallization of antiparallel-posited copolymers yielded crystallites near the block junction, which are relatively small and less stable due to their local dilution suppressing their melting points. Similar to the case of spider dragline silks, two contrasting stabilities of crystallites in semicrystalline multiblock copolymers explain their good toughness. Our modeling approach paves the way toward a better understanding of the structure-property relationship in the semicrystalline thermoplastic elastomers.

Effect of hydrophilic block end groups and block junction on block copolymer self-assembly in solution.

Recent research suggests that the end groups of polymers can affect their self-assembly. However, the effect of end groups on the self-assembly of block copolymers in solution remains unclear, and thus far, only micelle–vesicle transformations have been achieved via end-group modification. Herein, we report that hydrophilic block end groups and the junction between two blocks can affect the solution self-assembly of block copolymers, leading to the formation of different morphologies, including vesicles, cubosomes, and hexosomes. Poly(ethylene glycol)-b-polystyrene (PEG-b-PS) with hydroxyl, methoxy, azido, or amino groups at the PEG chain ends was synthesized and self-assembled in solution via the cosolvent method. As a result, the morphology of the block copolymers transformed from vesicles to hexosomes upon increasing the end-group hydrophobicity. In addition, a morphological transition from cubosomes to vesicles was observed upon changing the junction from a triazole to an amide, and the interaction between the solvent and end groups significantly affected the self-assembly behavior.

Alkaline magmatism on Neo‐Tethyan extensional domains: Evidences from the Gejiu complex in Yunnan, China

The Gejiu alkaline complex (GAC) within the western part of the Youjiang Basin provides a window to investigate the evolution in the junction of Cathaysia, Yangtze and Indochina blocks. Here, we investigate the GAC in terms of their petrology, zircon U–Pb geochronology, whole‐rock geochemistry, and Sr–Nd isotopic data to gain insights into the origin and evolution of the alkaline magma. The GAC is lithologically composed of alkali syenites and feldspathoid syenites, in which some were altered into sericite syenites. Zircon U–Pb dating of the alkali syenites yielded an age of 85.03 ± 0.47 Ma, which is slightly older than the feldspathoid syenites. The alkali syenites and feldspathoid syenites are silica‐saturated and silica‐undersaturated, respectively, and are characterized by high alkalinity with K2O + Na2O of 11.55–17.08 wt% and Al2O3 of 18.57–22.49 wt%, low MgO of 0.11–1.39 wt%, weakly negative Eu anomalies, enrichments of LILEs such as Th and U, HFSEs like Zr and Hf but depletion of Ba, Sr, Nb, Ta, P, Ti, strongly fractionated LREEs to HREEs. Their uniform Sr–Nd isotope composition with initial 87Sr/86Sr = 0.708802–0.710571 and εNd(t) = −7.1 to −6.6 indicates that they were products of a homologous magma. They crystallized at c. 810–956°C and have a relatively high magmatic oxygen fugacity. Our geochemical and isotopic data proved that the GAC magma was derived from the low‐degree partial melting (&lt;10%) of a phlogopite‐bearing‐enriched mantle that was metasomatized by subducting sediments and originated possibly from the spinel and garnet transition zone at a depth of 60–80 km and a pressure of about 1.8–2.4 Gpa. The primary magma experienced protracted two‐stage crystal fractionation of clinopyroxene+amphibole and biotite+K‐feldspar, forming alkali syenites and feldspathoid syenites. Crustal contamination plays a negligible role in their formation. Considering previous tectonic studies, it was therefore proposed that the GAC formed in an extensional tectonic setting related to the Neo‐Tethyan tectonic regions during the Late Cretaceous.

Development of an Acid-Labile Ketal Linked Amphiphilic Block Copolymer Nanoparticles for pH-Triggered Release of Paclitaxel.

Here, we report on the construction of biodegradable poly(ethylene oxide monomethyl ether) (MPEO)-b-poly(ε-caprolactone) (PCL) nanoparticles (NPs) having acid-labile (acyclic ketal group) linkage at the block junction. In the presence of acidic pH, the nanoassemblies were destabilized as a consequence of cleaving this linkage. The amphiphilic MPEO-b-PCL diblock copolymer self-assembled in PBS solution into regular spherical NPs. The structure of self-assemble and disassemble NPs were characterized in detail by dynamic (DLS), static (SLS) light scattering, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). The key of the obtained NPs is using them in a paclitaxel (PTX) delivery system and study their in vitro cytostatic activity in a cancer cell model. The acid-labile ketal linker enabled the disassembly of the NPs in a buffer simulating an acidic environment in endosomal (pH ~5.0 to ~6.0) and lysosomal (pH ~4.0 to ~5.0) cell compartments resulting in the release of paclitaxel (PTX) and formation of neutral degradation products. The in vitro cytotoxicity studies showed that the activity of the drug-loaded NPs was increased compared to the free PTX. The ability of the NPs to release the drug at the endosomal pH with concomitant high cytotoxicity makes them suitable candidates as a drug delivery system for cancer therapy.

Scattering Function and Spinodal Transition of Linear and Nonlinear Block Copolymers Based on a Unified Molecular Model

This work uses a block copolymer architecture [(A′B)nA2]m to unify the scattering function and spinodal transition of typical AB-type block copolymers. The key roles of block number, junction points and asymmetry ratios of block length are (1) to determine the form factor of each block copolymer at the molecular scale; (2) to affect the entropy loss across the spinodal transition and may result in deflection of spinodal curves. The common features are validated in typical linear and nonlinear block copolymers, including AB diblock, asymmetric A′BA triblock, miktoarm stars of ABn, AnBn, (AB)n, (A′B)nA, A′BAm, and multi-graft combs of (BnA2)m and [(A′B)nA2]m. The explicit scattering functions and form factors of various block copolymers can be directly applied in radiation experiments (i.e. neutron or X-ray scattering) to unravel the effect of molecular architecture in solution and microphase separation in disordered melt. The molecular model used in this study is also helpful to guide the chemical synthesis to explore more potentially interesting block copolymers.

Dual-Location Dual-Acid/Glutathione-Degradable Cationic Micelleplexes through Hydrophobic Modification for Enhanced Gene Silencing.

Gene therapy holds great promise for the treatment of acquired genetic disorders such as cancer with reduced side effects compared to chemotherapy. For gene therapy to be successful, it is crucial to develop efficient and nontoxic gene carriers to overcome the poor in vivo stability and low cellular uptake of nucleic acid-based therapeutic agents. Here, we report a new and versatile approach exploring a combination of hydrophobic modifications and dual-stimuli-responsive degradation (SRD) for controlled gene delivery with amphiphilic block copolymer-based nanocarriers. The block copolymer, synthesized by atom transfer radical polymerization, is designed with an acid-labile acetal linkage at the block junction and a pendant disulfide group in the hydrophobic block. The incorporation of labile linkages enables both disulfide-core-cross-linking and dual-location dual-acid/reduction-responsive degradation (DL-DSRD). Furthermore, the disulfide linkages integrated as hydrophobic moieties facilitate the nucleic acids to condense into nanometer-sized micelleplexes through electrostatic interactions of pendant dimethylamino groups with the anionic phosphate groups of the nucleic acids. Our preliminary results demonstrate that the DL-DSRD approach through hydrophobic modification is a robust platform in the development of gene delivery systems with enhanced colloidal stability, reduced cytotoxicity, and improved gene transfection efficiency.

47CRT-D versus CRT-P: are we on the right track?

Abstract Introduction Implantable cardioverter defibrillators (ICD) and cardiac resynchronisation therapy (CRT) have both proven to reduce mortality in patients with heart failure (HF). However, randomised trials comparing CRT-pacemaker (CRT-P) vs CRT-defibrillator (CRT-D) are lacking. Understanding a patient’s primary mode of death is therefore important as this may guide the proper use of CRT systems and avoid risks that are associated with under -or overtreatment with an ICD. Purpose This study aims to analyse the mode of death and the occurrence of life-threatening ventricular arrhythmias (VAs) in patients who received a CRT-P or CRT-D. This may help in the future selection for an appropriate cardiac device in patients with HF. Methods Patients with HF undergoing CRT-P or CRT-D implantation in a tertiary hospital between January 2008 and December 2018 were retrospectively evaluated. CRT indications were in compliance with the ESC guidelines. The decision to implant CRT-D or CRT-P in primary prevention was left at the discretion of the treating physician but was based on ESC clinical guidance. Life threatening VAs (sustained ventricular tachycardia &amp;gt; 30s not requiring therapy or appropriate therapy for VAs) and mode of death were analysed. Results 511 patients were implanted with a CRT (CRT-D/CRT-P; n = 311/200) of which 410 (CRT-D/CRT-P; n= 245/165) were followed in our centre for 63,5 ± 38,1 months. Patients with CRT-P were older (77,6 ± 8,1 vs 66,8 ± 9,5 years; p &amp;lt;0,001), more often female (39,4 vs 26,9%; p 0,006), had more a non-ischaemic cause (61,2 vs 44,9%; p 0,001) and a significant higher comorbidity burden. They also received less treatment with neurohumoral blockers. Baseline LVEF was higher in the CRT-P group (33,1 ± 8,9 vs 28,0 ± 7,6%, p &amp;lt;0,001). 6 months follow-up showed a similar increase in LVEF in the CRT-P vs CRT-D group (+10,3 ± 9,6 vs +11,4 ± 10,8%, p 0,38). Main reasons to choose for CRT-P were RV-pacing induced cardiomyopathy (CMP) (26,1%), multiple comorbidities (18,8%), HF complicated by high degree AV block or AV junction ablation (18,2%), non-ischaemic CMP with suspected good CRT response (10,3%), age (7,3%), other (19,3%). 6/165 patients with CRT-P (3,6%), of which 5 were detected by remoted telemonitoring, vs 51/245 with CRT-D (20,8%) experienced episodes of life-threatening arrhythmias (p &amp;lt;0,001). All-cause mortality was higher in the CRT-P vs CRT-D group (36,4 vs 25,3%, p 0,005). However, the CRT-P group had a predominant non-cardiac mode of death (70,9 vs 43,3%, p &amp;lt;0,001). Death secondary to a tachyarrhythmic event was present in only 1 patient (1,7%) in the CRT-P group. Conclusions Guided by clinical parameters and presence of competitive non-cardiac causes of death, adequate decision between CRT-P or CRT-D implantation can be made. In our cohort, sudden cardiac death in the CRT-P group occurred only once. Remote monitoring is able to identify a subgroup of patients potentially benefiting from an upgrade from CRT-P to CRT-D.

Monomer Sequence Effects on Interfacial Width and Mixing in Self-Assembled Diblock Copolymers

Monomer sequence is shown to directly control interfacial and in-domain mixing in lamellar polystyrene-b-polypeptoid diblock copolymers, where the polypeptoid block is composed of precise sequences of highly segregating (polar) and compatibilizing (nonpolar) repeat units. With monomer-by-monomer sequence control, the effects of blockiness, comonomer distribution, and taper direction on the interfacial width are measured with small-angle X-ray scattering and further understood through simulations with self-consistent field theory. When compatibilizing groups are distributed along the polypeptoid chain, the presence of neighboring polar groups suppresses interfacial mixing and causes the interfacial width to narrow, especially for the blocky sequence. When compatibilizing groups are tapered from the block junction, they are strongly localized at the domain interface and both interfacial mixing and interfacial width are increased. Consequently, tapered sequences produce more pure domain centers, while the distributed materials have compatibilizing groups located throughout the polypeptoid domain, encouraging more polystyrene to mix in. An analogous poly(n-butyl acrylate) system was synthesized to probe the effects of a different interaction parameter (χ). Similar trends with sequence were found but with smaller magnitudes due to the higher χ. This study shows that monomer sequence directly affects segmental mixing both at and away from the interface, with consequences for interfacial width and domain spacing. Along with the sequence-driven nonideal chain conformations shown recently, these combined sequence-specific effects determine the resulting geometry and thermal stability of the self-assembled lamellae, suggesting that comonomer sequence can be used to tailor self-assembling materials without changing the composition or chemistry.