Effect Of Block Length Research Articles

Performance Measurement and Optimization of Relays Used for 5G Ultra Reliable Low Latency Communication Network

The objective of this paper is to analyse and optimize the performance parameters of Relay nodes used in the finite block length (FBL) regime. A relaying system with a single Decode and Forward (DF) Relay is used for this purpose. Here using FBL, the performance parameters like coding rate, decoding error probability etc are obtained for different scenarios like without relay, with relay and using cooperative relaying. Effects of SNR and code Block length on performance parameters are analyzed. To enhance the performance of the Relay in URLLC scenario, power distribution between source and Relay node is optimized using evolutionary algorithms such as Multi-Objective Particle Swarm Optimization (MOPSO) and Infeasibility Driven Evolutionary Algorithm (IDEA). Low error probability and high throughput at the desired block length and power were the optimization goals. After using both the algorithms, the optimized Relay has shown improvement in performances like throughput (coding rate) and decoding error probability. It is also observed that IDEA optimization approach is found to be more efficient than MOPSO to provide optimum design parameters.

Influence of semi‐crystalline poly(ε‐caprolactone) and non‐crystalline polylactide blocks on the thermal properties of polydimethylsiloxane‐based block copolymers

AbstractPoly(A)‐block‐poly(B), poly(A)‐block‐poly(B)‐block‐poly(A) and B(A)2 block copolymers were prepared through coordinated anionic ring‐opening polymerization of ε‐caprolactone (CL) and lactic acid (LA) using hydroxy‐terminated polydimethylsiloxane (PDMS) as initiator. A wide range of well‐defined combinations of PDMS‐block‐PCL and PDMS‐block‐PLA diblock copolymers, PCL‐block‐PDMS‐block‐PCL and PLA‐block‐PDMS‐block‐PLA triblock copolymers and star‐PDMS(PCL)2 copolymers were thus obtained. The number‐average molar masses and the structure of the synthesized block copolymers were identified using various analytical techniques. The thermal properties of these copolymers were established using differential scanning calorimetry. Considering PDMS‐block‐PCL copolymers, the results demonstrate the complex effect of polymer architecture and PCL block length on the ability of the PDMS block to crystallize or not. In the case of diblock copolymers, crystallization of PCL blocks originated from stacking of adjacent chains inducing the extension of the PDMS block that can easily crystallize. In the case of star copolymers, the same tendency as in triblock copolymers is observed, showing a limited crystallization of PDMS when the length of the PCL block increases. In the case of PDMS‐block‐PLA copolymers, melting and crystallization transitions of the PLA block are never observed. Considering the diblock copolymers, PDMS sequences have the ability to crystallize. © 2019 Society of Chemical Industry

Effect of Block Length and Stereocomplexation on the Thermally Processable Poly(ε-caprolactone) and Poly(Lactic acid) Block Copolymers for Biomedical Applications

The current research concentrates on the synthesis of linear block copolymers with their backbone consisting of hard and soft segments, that is, poly(L-lactic acid) (PLLA)/ poly(D-lactic acid) (PDLA) and poly(e-caprolactone) (PCL), with the detailed investigation of the effect of block length on the thermal, mechanical, and crystallization behavior followed by their processing and biocompatibility evaluation. In the current work, sequential ring opening polymerization has been employed wherein PCL is used as a macroinitiator for the synthesis of diblock (PCL-PDLA and PCL-PLLA) and stereotriblock copolymers (PCL-PLLA-PDLA) of targeted molecular weight, which is confirmed by 1H NMR spectroscopy. The block length of PCL, in the case of diblock copolymer, is fixed; however, that of PLLA or PDLA is varied, and the enantiomeric blends thereof are made to achieve the merits of stereocomplexation. The length of the individual blocks is the same in the case of stereotriblock copolymer. The presence of two crystall...

Template-Free Self-Assembly of Artificial De Novo Viral Coat Proteins into Nanorods: Effects of Sequence, Concentration, and Temperature.

The self-assembly of protein polymers is a promising route to prepare sophisticated functional nanostructures. However, the interplay between protein self-assembly by itself and its co-assembly with a template is not well understood. Silk-based protein polymers that co-assemble with DNA to form rod-like artificial viruses are herein developed and the effects of silk block length, concentration, and temperature in the self-assembly of the proteins alone are characterized by using a combination of bulk dynamic light scattering (DLS) and single-molecule atomic force microscopy (AFM). Protein nanorods were slowly formed (up to hours) through the interaction of the silk-like blocks. The proteins present a silk-length dependent critical elongation concentration, and above it the amount and size of nanorods rapidly increase. Temperature-dependent light scattering data was adequately fitted into a cooperative model of nucleation-elongation. These results are also important to understand the self-assembly of designed viral coat proteins with DNA templates to form artificial virus-like particles and help us to define general guidelines to design proteins with the ability to precisely organize matter at the nanoscale.

Effect of Block Length and Side Chain Length Ratios on Determining a Multicompartment Micelle Structure

Previous work has identified the importance of the lipophilic-fluorophilic block length ratio in predicting the morphology of linear lipophilic-hydrophilic-fluorophilic (hereafter referred to as BAC) micelle systems. Here, a generalized form of this structural parameter is developed that makes no assumption of BAC triblock co-polymer linearity, while still providing accurate predictions of the micelle morphology. The morphologies of BAC micelles formed by triblock co-polymers with or have similar features, with the only notable difference being an inversion of the lipophilic and fluorophilic regions. A destabilization of the single-core micelle structure occurs as approaches unity from either direction. Finally, the extent to which the micelle morphology depends on the polymer architecture instead of the composition alone is examined, with a decreased patchiness observed in BAC systems with very long block lengths. Through the modification of both the -value and the polymer architecture, the micelle morphology can be effectively tuned for use in immobilized catalysis and nanoreactor applications.

Controlled synthesis of polymethylene-b-poly(ethylene glycol) as well as its crystallization and self-assembly behavior

Polymethylene-b-poly(ethylene glycol) (PM-b-PEG) with different block length ratio was synthesized by a combination of polyhomologation and coupling reaction. The effect of hydrophilic and hydrophobic block length on the crystallization process and self-assembly behavior of PM-b-PEG was self-assembled were investigated. The results showed that with the increase of methylene units, the crystallization temperature of PM block raised from 54.59 °C to 70.93 °C gradually, while that of the PEG block reduced from 17.54 °C to 15.23 °C. In addition, the amphiphilic PM-b-PEG was self-assembled into star-like micelles in water, and its diameter extended from 98.2 nm to 151.9 nm as the block length of hydrophobic PM increased from 30 to 70. And the micelles also exhibit super stability when the concentration of copolymer precursor is 0.50 ∼ 0.90 mg/ml and the storage temperature lies in the range of 25 ∼ 60 °C.

Thermal and mechanical properties of highly flexible poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) bioplastics: Effects of poly(ethylene glycol) block length and chain extender

The brittleness of poly(L-lactide) (PLLA) bioplastic is the main disadvantage for practical applications. Herein, we report the synthesis of high-molecular-weight PLLA- b-poly(ethylene glycol)- b-PLLA (PLLA-PEG-PLLA) block copolymers by ring-opening polymerization of LLA. The highly flexible PLLA-PEG-PLLAs were prepared by reactive melt blending with an epoxy-based chain extender formed as long-chain branched structures. The effects of PEG block length and content of chain extender were investigated. The results showed that the chain extension reaction reduced crystallinities of the PLLA-PEG-PLLAs. All the chain-extended PLLA-PEG-PLLA films had no phase separation. The lower crystallinities of PLLA-PEG-PLLA films obtained with higher contents of chain extender enhanced the film drawability. The longer PEG block length resulted in higher strain at break and lower stress at the break of PLLA-PEG-PLLA films. These chain-extended PLLA-PEG-PLLAs have potential for use as highly flexible bioplastics.

A piezoelectric cantilever with novel large mass for harvesting energy from low frequency vibrations

The piezoelectric cantilever with a large proof mass is a classic vibration energy harvesting structure. In this study, in order to harvest much more energy from low frequency vibration in the finite volume, a novel L type mass block is proposed and compared with a traditional rectangular mass block for the piezoelectric cantilever. A theoretical modeling of lumped parameter system is carried out considering the effect of mass block length on mass, stiffness and damping. A series of PZT bimorph cantilevers with brass proof mass prototypes are fabricated for the experimental verification. Their eigenfrequency and maximum piezoelectric power output are analyzed by the experiment and simulation. The piezoelectric cantilever with L type mass block avoids the weakness of decreasing the effective length of piezoelectric cantilever, and has lower eigenfrequency and larger piezoelectric power output than that with rectangular mass block. Its piezoelectric power output of 192 mW/(g2) can be obtained at the low resonant frequency of 18.1 Hz and the optimal load impedance of 5kΩ, and the unit volume power density is as high as 24.6 mW/(cm3×g2).

Effect of Corona Block Length on the Structure and Chain Exchange Kinetics of Block Copolymer Micelles

The effect of corona block length on micelle structure and molecular chain exchange kinetics has been investigated for a series of dilute poly(styrene)-b-poly(ethylene-alt-propylene) (SEP) diblock copolymer micelles with constant PS core block length (⟨Ncore⟩ ≈ 255) but different PEP corona block lengths (⟨Ncorona⟩ = 256–2080), using a combination of dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and time-resolved small-angle neutron scattering (TR-SANS). Smaller core radii and aggregation numbers, but significantly thicker corona layers (proportional to Ncorona0.7), were observed with increasing corona block length. Furthermore, 2 orders of magnitude more rapid chain exchange was observed in SEP micelles with the longest corona block compared to the shortest. This effect is attributed to the entropic gain arising from the relief of corona chain stretching upon chain expulsion. We further extend a previous theoretical model by explicitly including a corona term associated with the en...

Stereocomplexation and mechanical properties of polylactide-b-poly(propylene glycol)-b-polylactide blend films: Effects of polylactide block length and blend ratio

In the present work, poly(propylene glycol) (PPG) was block copolymerized to form polylactide-poly(propylene glycol)-polylactide (PL-PPG-PL) triblock copolymers for preparing flexible stereocomplex PL (scPL) blend films. The scPL blend films were prepared by solution blending of poly(L-lactide)-PPG-poly(L-lactide) (PLL-PPG-PLL) and poly(D-lactide)- PPG-poly(D-lactide) (PDL-PPG-PDL) triblock copolymers before film casting. The influences of PL end-block lengths (2 × 104 and 4 × 104 g/mol) and blend ratios (75/25, 50/50 and 25/75 W/W) on the stereocomplexation and mechanical properties of the blend films were evaluated. From DSC and WAXD results, the 50/50 blend films had complete stereocomplexation. Phase separation between the scPL and PPG phases was not observed from their SEM images. The tensile stress and elongation at break increased with the sterecomplex crystallinities and PL end-block lengths. The PPG middle-blocks enhanced elongation at break of the scPL films. The results showed that the PL-PPG-PL triblock structures did not affect stereocomplexation of the PLL/PDL block blending. In conclusion, the phase compatibility and flexibility of the scPL films were improved by PPG block copolymerization.

Thermal performance of liquid cooling based thermal management system for cylindrical lithium-ion battery module with variable contact surface

In this paper, a novel liquid cooling based thermal management system for the cylindrical lithium-ion battery module with variable contact surface is designed. Contact surface size is determined by aluminum block length. The cooling system relies on aluminum block which can effectively transfer heat from battery to cooling water. A battery module with six cells along flow channel is chosen to study the effects of aluminum block length and velocity on the thermal performance in the way of simulation. Three change types of contact surface are studied and their performance are compared with the system with constant contact surface at different inlet velocities. The results indicated that the system with variable contact surface is superior to the system with constant contact surface. It can significantly improve temperature uniformity. When inlet velocity is 0.05m/s, the maximum temperature can decrease to the same value and temperature difference decreases by 6%, 14% and 28%. Finally, an optimal design is presented with system weight, pump power consumption and cooling performance taken into consideration.

Chain exchange kinetics between linear ABA-type triblock copolymer micelles

Chain exchange kinetics between triblock block copolymers of ABA-type with end block being soluble in solvent is investigated using dissipative particle dynamics simulations for the first time. In such micelles, the polymer conformation is believed to play an important role. Our simulations find that a majority of polymer chains take loop (bend) conformations within the micelle, and unimer expulsion is the dominant mechanism for exchange. The chain exchange follows a first-order kinetic process, for which the characteristic time τ increases with both core and corona block lengths, showing a qualitative agreement with the literature. While the strong effect of core block length is due to an increase in activation energy, the marginal effect of corona block length is attributable to the re-insertion of an escaping chain into the same micelle. Re-insertion is favored because of greater resistance for a chain to escape a thicker corona.

Autonomous unimer-vesicle oscillation by totally synthetic diblock copolymers: effect of block length and polymer concentration on spatio-temporal structures.

In this study, factors controlling autonomous vesicle oscillations exhibited by self-oscillating diblock copolymers were investigated. The self-oscillating diblock copolymer contains poly(ethylene oxide) (PEO) as the hydrophilic block and a random copolymer composed of N-isopropylacrylamide (NIPAAm) with side chains of ruthenium tris(2,2'-bipyridine) (Ru(bpy)3), which catalyzes the Belousov-Zhabotinsky (BZ) reaction, as the self-oscillating block. Recently, our group has reported that a diblock copolymer exhibits a unique autonomous disintegration and reconstruction of the vesicles driven by the periodic redox changes of Ru(bpy)3 in a catalyst-free BZ reaction solution. Nevertheless, the effect of the diblock copolymer architecture on the structure of the vesicles under equilibrium conditions, as well as their oscillation properties under non-equilibrium conditions, has not been clarified thus far. Hence, self-oscillating diblock copolymers with different block lengths were systematically synthesized, and the effects of the block length and polymer concentration on the spatio-temporal vesicle structures were comprehensively discussed.

Interactions of Pluronic nanocarriers with 2D and 3D cell cultures: Effects of PEO block length and aggregation state

This work reveals how the physicochemical properties of Pluronic block copolymers influence significantly their interactions with cancer cells, whether in monolayer or spheroid cultures, and how different clinical applications can be foreseen.Two-dimensional (2D) and three-dimensional (3D) cell culture models were used to investigate the interactions of Pluronic carriers with different PEO block length and aggregation state (unimers versus cross-linked micelles) in HeLa and U87 cancer cells. Stabilized micelles of Pluronic P94 or F127 were obtained by polymerization of a crosslinking agent in the micelles hydrophobic core. Nanocarriers were functionalized with a fluorescent probe for visualization, and with a chelator for radiolabeling with Indium-111 and gamma-quantification.The 2D cell models revealed that the internalization pathways and ultimate cellular localization of the Pluronic nanocarriers depended largely on both the PEO block size and aggregation state of the copolymers. The smaller P94 unimers with an average radius of 2.1nm and the shortest PEO block mass (1100gmol−1) displayed the highest cellular uptake and retention.3D tumor spheroids were used to assess the penetration capacity and toxicity potential of the nanocarriers. Results showed that cross-linked F127 micelles were more efficiently delivered across the tumor spheroids, and the penetration depth depends mostly on the transcellular transport of the carriers. The Pluronic P94-based carriers with the shortest PEO block length induced spheroid toxicity, which was significantly influenced by the spheroid cellular type.

A flexible Mth power carrier phase estimation algorithm for coherent optical receiver

Although Mth power carrier phase estimation (PE) algorithm has been investigated intensively in coherent optical phase-shift-keying (PSK) system, block length effect impacts system performance and increases hardware complexity. In this paper, a flexible Mth power carrier PE algorithm is proposed to remove the effect of block length on system performance. We take into account the time-varying phase noise, instead of the assumption of constant phase noise over the entire observation interval. The weighted factors obtained from maximum likelihood method are introduced to eliminate the block length effect. Furthermore, we derive the analytical expression of phase error variance for the performance prediction of coherent receiver with the flexible Mth power. Bit error ratio (BER) performance of coherent receiver is evaluated and compared through both theoretical derivation and Monte Carlo simulation. The results show that by using the flexible Mth power algorithm, signal noise ratio (SNR) improvement over conventional Mth power algorithm with fixed block length of 20 and 40 at BER of 10−5 is 0.47dB and 2.18dB, when the linewidth per laser is 2MHz. By employing our flexible Mth power algorithm, SNR improvement over conventional Mth power algorithm with optimum block length will be larger as increasing laser linewidth . It means our flexible Mth algorithm is more effective for mitigating phase noise than the conventional Mth power algorithm.

Dependence of aggregation behavior on concentration in triblock copolymer solutions: The effect of chain architecture.

Using the self-consistent field lattice technique, the effects of concentration and hydrophobic middle block length (where the chain length remains constant) on aggregation behavior are studied in amphiphilic symmetric triblock copolymer solutions. The heat capacity peak for the unimer-micelle transition and the distribution peaks for the different degrees of aggregation for micelles and small aggregates (submicelles) are calculated. Analysis of the conducted computer simulations shows that the transition broadness dependence on concentration is determined by the hydrophobic middle block length, and this dependence is distinctly different when the length of the hydrophobic middle block changes. Different size for small aggregates simultaneously appear in the transition region. As temperature decreases, the number of different size small aggregates for the large hydrophobic middle block length first ascends and then descends in aggregation degree order. These results indicate that any transition broadness change with concentration is related to the mechanism of fragmentation and fusion. These results are helpful for interpreting the aggregation process of amphiphilic copolymers at equilibrium.

Re-assembly behaviors of block copolymer micelles on substrates: effects of block length and interaction force

The re-assembly behaviors of amphiphilic polystyrene-b-poly(acrylic acid) (PS-b-PAA) diblock copolymer micelles were investigated using dynamic light scattering, transmission electron microscopy, and atom force microscopy. PS-b-PAA diblock copolymer self-assembled into spherical micelles with PS as shell and PAA as core in toluene. The micelle size increased with the PS block length in polymers containing a constant length of PAA block. With the PS block length increased, spherical micelles re-assembled various distinguished morphologies such as clusters, large compound micelles (LCMs), rings, and ribbon-like aggregations. In addition, the interaction forces between PS and different substrates were directly measured in toluene to further investigate the mechanism. The results indicated that the re-assembly occurred easily when the interaction force was weak. Systematic studies suggested that the micellar re-assembly behaviors on a flat surface were strongly dependent on the block length and interaction between micelles and substrates. Delineation of these rules provides a novel pathway to the design of hierarchical materials.

Effects of Block Length and Membrane Processing Conditions on the Morphology and Properties of Perfluorosulfonated Poly(arylene ether sulfone) Multiblock Copolymer Membranes for PEMFC.

Perfluorosulfonated poly(arylene ether sulfone) multiblock copolymers have been shown to be promising as proton exchange membranes. The commonly used approach for preparation of the membrane is solvent casting; the properties of the resulting membranes are very dependent on the membrane processing conditions. In this paper, we study the effects of block length, selectivity of the solvent, and thermal treatment on the membrane properties such as morphology, water uptake, and ionic conductivity. DiMethylSulfOxide (DMSO), and DiMethylAcetamide (DMAc) were selected as casting solvents based on the Flory-Huggins parameter calculated by inversion gas chromatography (IGC). It was found that the solvent selectivity has a mild impact on the mean size of the ionic domains and the expansion upon swelling, while it dramatically affects the supramolecular ordering of the blocks. The membranes cast from DMSO exhibit more interconnected ionic clusters yielding higher conductivities and water uptake as compared to membranes cast from DMAc. A 10-fold increase in proton conductivity was achieved after thermal annealing of membranes at 150 °C, and the ionomers with longer block lengths show conductivities similar to Nafion at 80 °C and low relative humidity (30%).

Effect of Hydrophilic/Hydrophobic Block Ratio and Temperature on the Surface and Associative Properties of Oxyethylene and Oxybutylene Diblock Copolymers in Aqueous Media

Recent development in dispersion science and technology demands block copolymers with a variable block length and composition. To highlight that purpose, the surface active, associative, colloidal, and thermodynamic behavior of three diblock copolymers having different hydrophilic to hydrophobic ratio is reported here. Using surface tension and light scattering measurements, the micellization and adsorption behavior of polyoxyethylene and polyoxybutylene diblock copolymers of the type EmBn have been analyzed. Critical micelle concentration (CMC) and related thermodynamic parameters like free energy (ΔGmic), enthalpy (ΔHmic), and entropy (ΔSmic) of micellization were calculated from CMC value using the closed association model. Likewise, the surface active parameters, like surface excess concentration (Γ2), area per molecule (A2), and thermodynamic parameters such as free energy (ΔGads), enthalpy (ΔHads), and entropy (ΔSads) of adsorption of polymer at the air/water interface, were also calculated at various temperatures. Static and dynamic light scattering techniques were employed for the determination of the weight-average molar (Mw), association number (Nw), polymer–water interaction (A2), and micellar size in terms of hydrodynamic radii (Rh) of copolymer micelles. The effect of block length and solution temperature on the surface and micellar properties of these copolymers was also investigated.

Liquid Crystalline Phase Behavior of Well-Defined Cylindrical Block Copolymer Micelles Using Synchrotron Small-Angle X-ray Scattering

The structure and phase behavior of colloidal solutions of monodisperse rod-shaped micelles, of different lengths (ca. 300–2100 nm) and formed from poly(ferrocenylsilane)-block-polyisoprene (PFS-b-PI) diblock copolymers, have been investigated using synchrotron small-angle X-ray scattering. The dimensions of the crystalline PFS core, solvated PI corona, and the overall radial polydispersity were measured, and relationships between the characteristics of the constituent copolymers and the internal structure of the self-assembled micelles have been established. In addition, the effects of micelle length, length distribution, concentration, composition, and block length on the liquid crystalline phase behavior of the micelles have been determined. It was found that micelle dispersions exist in three distinct phases: isotropic, nematic, and hexagonally packed, depending predominantly on their concentration and aspect ratio. The results have also highlighted the importance of the coronal composition and structure in determining the high-concentration behavior of micelle dispersions.