Single Loop Research Articles

MP-453087-3 REMOVAL OF A CHRONICALLY-IMPLANTED MICRA LEADLESS VENTRICULAR – SINGLE CENTER EXPERIENCE

Leadless cardiac pacemakers (LPs) are an effective and safe alternative to transvenous pacemakers for single-chamber ventricular pacing. However, the feasibility of retrieving and replacing chronically implanted LPs is not well understood. We report an unique single center series of chronically implanted MICRA TPS™ leadless pacemakers. Since 2014 there were 227 MICRA LP devices implanted successfully to the right ventricle (RV) position. In 8 patients with average time of 685 ± 373 days retrieval procedure was indicated. The main indication for LP extraction was: a) pacemaker syndrome; b) battery depletion (in two patients together with WiSE EBR left ventricle (LV) co-implant); c) needs to upgrade VVI pacing for resynchronization therapy with LV systolic dysfunction. In all 8 patients we used MICRA delivery catheter with single loop 7 mm snare inserted into the central lumen of the original delivery catheter. Besides fluoroscopy we guided the retrieval procedure with intracardiac echocardiography (ICE). The retrieval procedure was successful in 7 out of 8 petients (87,5%). Average time of the index retrieval procedure was 118 ± 27 minutes and average fluoroscopy time was 26.6 ± 10.5 minutes. In the case with retrieval procedure failure (348 days after implant) we couldn’t snare the docking bottom of the device. In rest of the cases where we were able to snare it and connect with the delivery catheter cap, we were able to reach the insertion of the LP to the tissue and apply contratraction force with 100% success. When we analysed ICE images, the LP retrieval failure was associated with massive tissue overgrow around the device capsule. In 6 patients new MICRA TPS™ LP was implanted with excellent pacing parameters and optimal sensing and impedance during the same procedure. In one patient we implanted CRT-D transvenous system due to LV dysfunction. This series demonstrates the feasibility of retrieval of even long-term chronically-implanted MICRA LPs. The dedicated retrieval system for LPs with anchors will be of interest when we can consider needs to exchange of LPs specifically in younger patients.

High Step-Up Gain Converter Based on Two-Phase Interleaved Coupled Inductor Without Right-Hand Plane Zero

This paper proposed a novel two-phase interleaved Coupled Inductor (CI) based high step-up gain converter without Right Half Plane (RHP) zeros for a wide operating range of duty cycle. A coupled inductor between input and output is used in the proposed converter to eliminate RHP zero. The energy of CI is transferred to output capacitor when switch is ON to eliminate RHP zero. Furthermore, the converter has a wide operating range to eliminate RHP zero with a coefficient coupling of CI near one. Thus, the converter achieves higher bandwidth and a wide range of control over output voltage. The small-signal model of proposed converter is derived to verify the proposed claim. The single loop voltage control is sufficient to regulate output voltage of the converter with a good stability margin and faster dynamic response for a wide range of load changes. In addition, proposed converter has a high voltage step-up gain and low voltage stress on switching devices compared to the boost converter. Moreover, interleaved operation at input side reduces ripple and increases power density. All theoretical findings are verified by simulation and experimental results. Experimental results are provided from implemented laboratory prototype of input voltage of 24 V to output voltage of 100 V and 200 W power.

Performance analysis of frequency selective reflectors based on rectangular loop pair for wideband applications

This paper presents performance analysis of single layered bandstop frequency selective surfaces (FSSs) for C-band and ultra-wideband (UWB) frequency ranges respectively. These FSSs are based on polarization dependent (PD) single rectangular loop pair (RLP). RLP arrays in square and rectangular grids are developed and simulated to evaluate signal rejection and reflection for incident transverse electric (TE) and transverse magnetic (TM) waves. Further, orthogonal patterns are printed back-to-back (BTB) on dielectric substrate to study wave propagation and effect on wave polarization. Non-linearities in the reflection phase of BTB arrays are then mitigated by printing orthogonal FSS arrays on the same side of the dielectric substrate. The equivalent circuit models (ECMs) of these FSSs are also presented to predict their transmission characteristics. Later, two FSSs with wideband and ultra-wideband rejection capability are developed and experiments are carried out. The array of merged RLP arranged in square grid exhibits stopband from 4.5 GHz to 8.4 GHz with polarization independence (PI) and it is angularly stable while merged array of RLP arranged in rectangular grid exhibit ultra-wide stopband from 2.3 GHz to 11.5 GHz but it is not angularly stable. The measured transmission responses of all FSSs proposed here are close to simulated results.

Enhanced magnetostriction of Co–Ni-ferrite composites derived from hard (CoFe2O4) and soft (NiFe2O4) magnetostrictive phases

We report on the enhanced magnetostrictive characteristics of composites derived from the hard cobalt ferrite (CoFe2O4; CFO) and soft nickel ferrite (NiFe2O4; NFO) materials. The CFO, NFO and CFO-NFO (CNFO) mixed composites (25NFO + 75CFO, 50NFO + 50CFO and 75NFO + 25 CFO) were synthesized by employing a cost-effective and eco-friendly glycine-nitrate autocombustion method. The CFO, NFO and their mixed composites were evaluated to assess their phase purity, surface morphology, magnetic properties, and magnetostrictive characteristics. The X-ray diffraction (XRD) and electron microscopy analyses revealed that the CFO and NFO nanomaterials were phase pure, porous in nature, and nano-sized with average crystallite size of 73 nm (CFO) and 69 nm (NFO). Subsequently, the Co–Ni-ferrite composite made from CFO and NFO in equal quantity by sintering at 1200 °C indicate that the lattice parameter, a, of the composite lies in between the lattice parameters of respective components (CFO-8.390 Å and NFO-8.343 Å) indicating that both phases co-exists as single-phase in the composite. The grains of the sintered compounds are nearly spherical shape with the average sizes ∼670 nm, ∼550 nm and ∼560 nm, respectively, for CFO, NFO and 50NFO +50CFO composite. Due to grain growth upon sintering, magnetizations of the sintered CFO and NFO nanomaterials are higher than that of as-synthesized samples. Interestingly, the magnetization curves of sintered CNFO composites exhibit symmetric nature (single loop), where their magnetization lies in between the magnetizations of NFO and CFO phases, indicating a proper exchange coupled between the two phases. The composites demonstrate better magnetostriction at lower magnetic fields than the parent sintered CFO and NFO samples. At an applied magnetic field of 2 kOe, the obtained magnetostriction value for 50NFO +50CFO composite (−120 ppm) is nearly 500% higher than that of CFO (−20 ppm) and 300% higher than that of NFO (−30 ppm). The structure-phase-property correlation established in these composites expected to provide a road-map for their possible applications in electromagnetic devices.

Multi-variable extremum seeking control for high temperature heat pump system incorporating double refrigerant injection

The use of refrigerant injection technology to enhance the heating efficiency of heat pumps with larger temperature lifts is becoming more common. Heat pumps with double refrigerant injection loops have better energy efficiency than traditional ones with single refrigerant injection loops. A multi-variable extremum seeking control (ESC) strategy for a high-temperature heat pump system with double refrigerant injection technology is proposed in this study. A Modelica-based dynamic simulation model of the considering system is established in Dymola, and a co-simulation with the proposed ESC strategy is built to validate the effectiveness of this control strategy to minimize power consumption. The strategy uses compressor power consumption as the feedback. The effective throttling area of the upper and lower EEVs is adjusted by a PI controller to manipulate the low and high-pressure vapor injection pressures. Three scenarios were simulated for control: stable, step curve, and freely variable heat source temperature conditions. The simulation results demonstrate that the multi-variable ESC has excellent convergence performance and confirm its effectiveness in searching for the optimal operating point.

An ultra-high sensitivity methane gas sensor based on Vernier effect in two parallel optical fiber Sagnac loops

Methane gas sensing has attracted great interest for its applications in agriculture production, industrial manufacturing, medical diagnosis, and environmental monitoring. In this paper, we proposed an ultra-high sensitivity methane gas sensor based on Vernier effect in two parallel optical fiber Sagnac loops. The reference arm contained a polarization maintaining photonic crystal fiber (PM-PCF), while sensing arm consists of a methane gas sensitive film coated PM-PCF. Vernier effect (VE) was generated and as a result the sensitivity was improved by multiple times. The finite element method (FEM) was used to assess the methane gas sensor’s sensing capabilities. According to the numerical simulation, the average sensitivity based on two parallel Sagnac loops in the methane gas concentration of 0-3.5% was 197.775 nm/%, which was 5.5 times in contrast to a single Sagnac loop. To our best knowledge, we presented the methane gas sensor based on VE in two parallel optical fiber Sagnac loops for the first time. The designed optical fiber methane gas sensor possessed the merits of ultra-high sensitivity, providing helpful guidelines for the fabrication of high-performance methane gas sensors.

The ChvG-ChvI Regulatory Network: A Conserved Global Regulatory Circuit Among the Alphaproteobacteria with Pervasive Impacts on Host Interactions and Diverse Cellular Processes.

The ChvG-ChvI two-component system is conserved among multiple Alphaproteobacteria. ChvG is a canonical two-component system sensor kinase with a single large periplasmic loop. Active ChvG directs phosphotransfer to its cognate response regulator ChvI, which controls transcription of target genes. In many alphaproteobacteria, ChvG is regulated by a third component, a periplasmic protein called ExoR, that maintains ChvG in an inactive state through direct interaction. Acidic pH stimulates proteolysis of ExoR, unfettering ChvG-ChvI to control its regulatory targets. Activated ChvI among different alphaproteobacteria controls a broad range of cellular processes, including symbiosis and virulence, exopolysaccharide production, biofilm formation, motility, type VI secretion, cellular metabolism, envelope composition, and growth. Low pH is a virulence signal in Agrobacterium tumefaciens, but in other systems, conditions that cause envelope stress may also generally activate ChvG-ChvI. There is mounting evidence that these regulators influence diverse aspects of bacterial physiology, including but not limited to host interactions.

Intelligent electromagnetic mapping via physics driven and neural networks on frequency selective surfaces

The high mapping efficiency between various structures and electromagnetic (EM) properties of frequency selective surfaces (FSSs) is the state-of-the-art in the EM community. The most straightforward approaches for beam analysis depend on measurements and conventional EM calculation methods, which are inefficient and time-consuming. Equivalent circuit models (ECMs) with excellent intuitiveness and simplicity have been put forward extensively. Despite several applications, bottlenecks in ECM still exist, i.e. the application scope is restricted to narrow bands and specific structures, which is triggered by the ignorance of EM nonlinear coupling. In this study, for the first time, a lightweight physical model based on neural network (ECM-NN) is proposed , which exhibits great physical interpretability and spatial generalization abilities. The nonlinear mapping relationship between structure and beam behavior is interpreted by corresponding simulations. Specifically, two deep parametric factors obtained by multi-layer perceptron networks are introduced to serve as the core of lightweight strategies and compensate for the absence of nonlinearity. Experimental results of single square loop (SL) and double SL indicate that compared with related works, better agreements of the frequency responses and resonant frequencies are achieved with ECM-NN in broadband (0–30 GHz) as well as oblique incident angles (0°–60°). The average accuracy of the mapping is higher than 98.6%. The findings of this study provide a novel strategy for further studies of complex FSSs.

Cord Length, Umbilical Artery Lactate Concentration and Perinatal Outcomes of Babies with Nuchal Cord at Ile-Ife, Nigeria

Background: There is inconclusive evidence on the relevance of the nuchal cord in obstetric practice. Objectives: This study aims to evaluate the umbilical artery lactate concentration and perinatal outcomes of babies born with a nuchal cord. Methods: In a cross-sectional study at the Obafemi Awolowo University Teaching Hospital, babies born with a nuchal cord at term and matched controls without a nuchal cord were recruited between January 2017 and December 2018. Gestational age at delivery, meconium-stained liquor, foetal heart rate abnormalities, Caesarean section rates, cord lengths and umbilical artery lactate concentrations were compared. The umbilical artery lactate concentration was assayed with the Lactate-Plus®; neonatal acidosis was defined as cord lactate concentration > 4.9mmol/L. Results: One hundred and forty-four babies with nuchal cords and 144 controls were recruited. The prevalence of nuchal cord was 3.4%, with 80% of the babies having a single loop. Babies with nuchal cords had longer mean cord length (57.7cm vs 45.4cm; p<0.01), higher mean umbilical artery lactate (4.93mmol/L vs 3.48mmol/L; p = 0.04), meconium-stained liquor (16% vs 3.2%; Relative risk = 4.6), more babies with Apgar score <7 at fifth minute (9 versus 4 babies) and increased perinatal mortality (55.5/1000 births vs 13.8/1,000 births; Relative risk = 4). There was a positive correlation between cord length and the number of nuchal loops (r = 0.5, p<0.01). Conclusions: Nuchal cord is associated with abnormal cord lactate concentration and adverse perinatal outcomes. Prenatal reporting may enhance intrapartum surveillance and improve perinatal outcomes.

Examination of Low-Cyclic Fatigue Tests and Poisson's Ratio Depending on the Different Infill Density of Polylactide (PLA) Produced by the Fused Deposition Modeling Method.

This article examines the impact of fatigue cycles on polylactide samples produced by 3D printing using the FDM method. Samples were printed in three infill degree variants: 50%, 75% and 100%. To compere the influence of infill degree on PLA properties, several tests, including the uniaxial tensile test, the low-cycle fatigue test, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), were conducted. Poisson's ratio has also been studied. Single hysteresis loops were summed to obtain the entire low-fatigue cycle. The infill of density influenced all compared mechanical parameters. The decrease in infill degree caused the reduction of Young's modulus and shear modulus. For a 100% degree of sample infill, a higher number of transferred load cycles were observed compared to PLA with 75% and 50% of infill. Additionally, the value of the transferred cyclic load before fatigue failure and the dissipation of mechanical energy was the highest for 100% of infill. It is also worth noting that fatigue tests can positively affect the appearance of the PLA structure. Obviously, it depends on the number of load cycles and the infill density. It causes that if the goal is to transfer as much load as possible over a long period of time, the maximum filling of the printed element should be used.

Numerical Modelling of Flow in Fluidic Oscillator

The systems with fluidic oscillators are intensively studied nowadays because the oscillatory flow can increase heat and mass transfer and decrease energy dissipation. Fluidic oscillators produce an active-type mixing enhancement but in a passive manner as they do not require any moving parts. They convert steady pressurized inlet flow to oscillatory or pulsatile flow at an outlet without the need for external power. In general, there are many types of fluidic oscillators, categorized by the underlying mechanism to create oscillatory output behaviour. The fluidic oscillator with the single feedback loop is analysed in this paper. A numerical simulation of oscillating flow is performed and two approaches for modelling flow, RANS, and LES are applied especially. The results of numerical simulation are compared with experimental measurement. The analysis is focused on pressure drop and oscillation frequency dependent on the inlet conditions. The energy spectrum of oscillating flow is analysed using discrete Fourier transform.

Defect Line Coarsening and Refinement in Active Nematics.

Active matter is naturally out of equilibrium which results in the emergence of diverse dynamic steady states, including the omnipresent chaotic state known as the active turbulence. However, much less is known how active systems dynamically depart out of these configurations, such as get excited or damped to a different dynamic steady state. In this Letter, we demonstrate the coarsening and refinement dynamics of topological defect lines in three-dimensional active nematic turbulence. Specifically, using theory and numerical modeling, we are able to predict the evolution of the active defect density away from the steady state due to time-dependent activity or viscoelastic material properties, establishing a single length scale phenomenological description of defect line coarsening and refinement in a three-dimensional active nematic. The approach is first applied to growth dynamics of a single active defect loop, and then to a full three-dimensional active defect network. More generally, this Letter provides insight into the general coarsening phenomena between dynamical regimes in 3D active matter, with a possible analogy in other physical systems.

Hydronic flow path analysis on the thermal comfort performance of radiant cooling system

Construction and operation in the building sector account for more than 1/5th of global energy consumption. Moving on to an energy-efficient cooling technology and eco-friendly building material can lead to energy savings and a reduction in associated CO2 emissions. In the present study, an energy-efficient thermally activated building system (TABS) is integrated with eco-friendly building material, namely, glass fibre reinforced gypsum (GFRG). The proposed hybrid system is termed as thermally activated glass fibre reinforced gypsum (TAGFRG) system. This system is not only energy-efficient and eco-friendly but also provides better thermal comfort. An experimental room is constructed with the TAGFRG roof within the Indian Institute of Technology Madras campus, Chennai, i.e., in a tropical warm and humid climate zone. The TAGFRG roof has reinforcement in every third cavity with cooling pipes, while in the other two cavities, cooling pipes are embedded with air gap and partial reinforcement. The TAGFRG roof has four parallel loops of cooling pipelines, and each loop consists of one reinforcement zone (RZ) and two air gap zones (AZ1 and AZ2) in series. According to the water flow path in a single loop, various combinations of the flow path, i.e., RZ → AZ1 → AZ2, AZ1 → RZ → AZ2 and AZ1 → AZ2 → RZ, have been analyzed. According to the adaptive thermal comfort model, the water flow path has a negligible effect on thermal comfort. The average operative temperature for all the cases investigated varies between 28.1 and 29.2 °C. The operative temperature is always within the 90% band of thermal comfort, as per the adaptive comfort model.

Nondisturbing Extremum Seeking Control for Multiagent Industrial Systems

Industrial applications of extremum seeking control (ESC) can be a hit and miss affair. Although a gain in performance can be achieved, the dither applied to excite the system causes unwanted fluctuations in the performance of the system. The fluctuations in systems with a single extremum seeking loop are generally small. However, for systems with many extremum seeking loops, the fluctuations in each loop may add up to an intolerable amount of fluctuation in the total performance. In this article, we propose a method to cancel the dither-induced fluctuations in the overall system performance to a large extent by smartly constructing the dither signals in each extremum seeking loop using a centralized coordinator. The novelty of our method lies in the direct calculation of the dither signals that avoids the heavy computations required by other methods. Moreover, we provide a solvability analysis for the problem of cancelling dither-induced fluctuations in the total performance of the system. Furthermore, a complete stability analysis of the overall ESC scheme with dither coordination is given.

Design of a novel robust adaptive cascade controller for DC‐DC buck‐boost converter optimized with neural network and fractional‐order PID strategies

AbstractA cascade technique with two control loops is designed for a DC\DC Buck‐Boost converter that is a right half‐plane zero (RHPZ) structure called a non‐minimum phase system. This concept presents several challenging constraints for designing well‐behaved control techniques. Cascade controllers can provide various benefits compared with single loop controllers such as higher safety, higher robustness, and higher stability. This strategy assumes the system as a black‐box structure without the need for a mathematical model of the system. This benefit can decrease the computational burden and provides faster dynamics along with ease of implementation. This technique consisted of an outer Fractional‐order PID voltage controller tuned with the Antlion Optimizer (ALO) algorithm, which provides a reference current for the inner control loop of the Neural Network‐based LQR (NN‐LQR) controller. The basic principle in cascade controllers is a more rapid performance of the inner loop that has been satisfied with the NN‐LQR strategy, which optimizes and tunes the gains of the LQR controller and shows faster dynamics and higher robustness. It should be mentioned that the number of neurons is limited to 2 and 4 in each layer to decrease the computational burden with lower complexity. Also, the ALO algorithm is a modern nature‐inspired algorithm used to tune the PID gains with better results under‐constrained problems with diverse search spaces. Considering the negative impacts of various disturbances on a power converter, a Fractional‐order‐based PID (FO‐PID) control technique is a proper alternative since it shows higher robustness in load uncertainties along with better dynamical responses based on its extra degree of freedom. Moreover, to evaluate the superiority of this controller, two other controllers are designed using the PSO algorithm for PID and FO‐PID controllers. Finally, the presented cascade controller has been tested in various working conditions through simulation and experiment results.

Time-delay signature suppression in single loop optoelectronic oscillators based on sine hyperbolic nonlinear amplifier

Time-delay signature suppression in single loop optoelectronic oscillators based on sine hyperbolic nonlinear amplifier

A flexible 8.5 MHz litz wire receive array for field-cycling imaging

Objectives. Low frequency coils present unique challenges as loop losses, component losses, and the supporting electronics can significantly degrade the signal-to-noise ratio (SNR). SNR may already be a limiting factor with MRI at low field (and frequency), therefore the minimization of additional loss is particularly important. If interactions between loops are managed, array coils can provide increased SNR, coverage, and potentially imaging speed. In this work, we investigate methods to characterise and preserve SNR from a low frequency coil array, allowing a more geometrically conforming array for quick, no-tune application with various anatomies. Approach. Single and multi-turn, 16.2 cm diameter litz wire loops were constructed and characterised for losses under various loading conditions. Low noise preamplifiers were acquired and characterized, as well as interfacing electronics were developed and evaluated. A bench level SNR test was implemented to observe the effects of tuning and loading on individual coils. The results were used to select a design for construction of a 6-channel, flex array coil. Main results. Ultra fine strand litz wire exhibited lower losses than equivalent diameter solid wire which should translate to improved SNR and provides the mechanical flexibility needed in a conforming array. Single turn loop losses were dominant under all loading conditions; however, 2 and 3 turn loops were body loss dominated under modest loading conditions. Preamplifier blocking achieved was well short of our design goal and critical overlaps became necessary for coil-to-coil interaction control. Our finished array, a 3-channel posterior array coil and a 3-channel anterior array coil, conforms nicely to various anatomies and is providing consistent results in various volunteer study trials. Significance. Receive coils are challenging at low fields as loop losses often limit the final SNR. This is exacerbated in an array coil as loops may be smaller and not coupled well to the body. In this work we have demonstrated that body loss dominance is possible with 16.2 cm loops at 8.5 MHz. We have optimized, built, and tested low noise interfacing electronics and characterized the SNR penalties as the tuning and loading is varied, a key parameter in a geometrically flexible array designed for rapid setup. The resultant 6-channel, general-purpose array is supporting various Field-Cycling Imaging studies where body habitus and anatomies require a flexible, adaptable array coil which can be quickly positioned and utilized.

Effects of parity, frustration, and stochastic fluctuations on integrated conceptual information for networks with two small-sized loops

This paper presents an evaluation of the system-level integrated conceptual information of a major complex for a small-scale network containing two loops in accordance with the integrated information theory 3.0 framework. We focus on the following parameters characterizing the system model: (1) number of nodes in the loop, (2) frustration of the loop, and (3) temperature controlling the stochastic fluctuation of the state transition. Effects of these parameters on the integrated conceptual information and conditions for major complexes formed by a single loop, rather than the entire network, are investigated. Our first finding is that parity of the number of nodes forming a loop has a strong effect on the integrated conceptual information. For loops with an even number of nodes, the number of concepts tends to decrease, and the integrated conceptual information becomes smaller. Our second finding is that a major complex is more likely to be formed by a small number of nodes under small stochastic fluctuations. On the other hand, the entire network can easily become a major complex under larger stochastic fluctuations, and this tendency can be reinforced by frustration. It is also shown that, although counterintuitive, the integrated conceptual information can be maximized in the presence of stochastic fluctuations. These results suggest that even when several small subnetworks are connected by only a few connections, such as a bridge, the entire network may become a major complex by introducing some stochastic fluctuations and by frustrating loops with an even number of nodes.

Surface-Bulk 2D Spin-Crossover Nanoparticles within Ising-like Model Solved by Using Entropic Sampling Technique

We model the thermal effects in different 2D spin-crossover (SCO) square lattices within the frame of the Ising-like model using Monte Carlo entropic sampling (MCES) method to enhance the scan of macrostates beyond the most probable thermal ones. In fact, MCES allows access to the metastable states, and it is then well adapted to study thermal hysteresis properties. In this contribution, we distinguish, for the first time, the interaction between molecules located in bulk at the surface and those connecting the bulk and surface regions of an SCO lattice. In addition, an extra ligand field contribution is assigned to surface molecules through an interaction parameter L. In the absence of environmental effects on surface nanoparticles, a single thermal hysteresis loop increasing with the lattice size is simulated with a unique bulk and surface equilibrium temperature Teq=Teqbulk= Teqsurf. When environmental effects are accounted for, a two-step behavior associated with two hysteresis loops of widths ΔTS (for the surface) and ΔTB (for the bulk) with an intermediate plateau 14 K wide is obtained in the thermal dependence of the high-spin (HS) fraction for the 6 × 6 lattice. The surface and bulk equilibrium temperatures are then different, both decreasing towards lower values, and the L parameter controls the three states’ behavior as well as the hysteresis loop interval. Size effects show that the equilibrium temperature is governed by the surface atoms for a small lattice size (5 × 5) and by the bulk atoms for a large lattice size (7 × 7). Moreover, a change in the size of the lattice results in a variation of the order–disorder (or Curie) temperature, TO.D., and the surface equilibrium temperature, Teq, while only TO.D. changes in bulk.

Achieving High Permittivity Paraelectric Behavior in Mesogen-Free Sulfonylated Chiral Polyethers with Smectic C Liquid Crystalline Self-Assembly

Ferroelectric liquid crystalline polymers (LCPs) with a high spontaneous polarization (Ps) are of great interest for the fabrication of advanced electronic devices. However, conventional ferroelectric LCPs typically exhibit low spontaneous polarization, only around 1 mC/m2. To increase the orientational polarization for ferroelectric LCPs, in this work, we designed mesogen-free comb-shaped LCPs based on isotactic polyepichlorohydrin, which contained highly dipolar sulfonyl groups (dipole moment of 4.5 Debye) in the side chains. The goal was to increase dipole density and induce ferroelectric switching. In this new series of mesogen-free LCPs, the sulfonyl groups were first moved away from the main chain to mitigate strong dipole–dipole interactions. Second, methyl-branched alkyl side chains were implemented to decrease the crystallizability and induce the Smectic C (SmC) self-assembly. Intriguingly, these SmC samples, for the first time, exhibited typical paraelectric behavior (i.e., slim S-shaped single hysteresis loops) with a high dielectric constant in the range of 20–30. Learning from the knowledge obtained from this study, we will be able to design new mesogen-free LCPs with tailor-made dipole–dipole interactions and realize ferroelectricity.