scholarly journals Crosslinker-Based Regulation of Swelling Behavior of Poly(N-isopropylacrylamide) Gels in a Post-Polymerization Crosslinking System

Gels ◽  
2019 ◽  
Vol 6 (1) ◽  
pp. 2
Author(s):  
Shohei Ida ◽  
Akimitsu Katsurada ◽  
Mitsuhiro Tsujio ◽  
Motoharu Nakamura ◽  
Yoshitsugu Hirokawa
Keyword(s):  
Solvent Effect ◽  
Structural Diversity ◽  
Soft Materials ◽  
Polymer Gels ◽  
Crosslinking Density ◽  
Swelling Behavior ◽  
Polymer Chains ◽  
Gel Properties ◽  
Alkyl Chains ◽  
Fundamental Understanding

A fundamental understanding of the effect of a crosslinker on gel properties is important for the design of novel soft materials because a crosslinking is a key component of polymer gels. We focused on post-polymerization crosslinking (PPC) system utilizing activated ester chemistry, which is a powerful tool due to structural diversity of diamine crosslinkers and less susceptibility to solvent effect compared to conventional divinyl crosslinking system, to systematically evaluate the crosslinker effect on the gel properties. A variety of alkyldiamine crosslinkers was employed for the synthesis of poly(N-isopropylacrylamide) (PNIPAAm) gels and it was clarified that the length of alkyl chains of diamine crosslinkers strongly affected the gelation reaction and the swelling behavior. The longer crosslinker induced faster gelation and decreased the swelling degree and the response temperature in water, while the crosslinking density did not significantly change. In addition, we were able to modify the polymer chains in parallel with crosslinking by using a monoamine modifier along with a diamine crosslinker. This simultaneous chain modification during crosslinking (SMC) was demonstrated to be useful for the regulation of the crosslinking density and the swelling behavior of PNIPAAm gels.

scholarly journals Mechanical Response of Two-Dimensional Polymer Networks: Role of Topology, Rate Dependence, and Damage Accumulation

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Konik Kothari ◽  
Yuhang Hu ◽  
Sahil Gupta ◽  
Ahmed Elbanna
Keyword(s):  
Mechanical Response ◽  
Polymer Networks ◽  
Soft Materials ◽  
Crosslinking Density ◽  
State Theory ◽  
Polymer Chains ◽  
Local Network ◽  
Network Characteristics ◽  
Rate Dependent

The skeleton of many natural and artificial soft materials can be abstracted as networks of fibers/polymers interacting in a nonlinear fashion. Here, we present a numerical model for networks of nonlinear, elastic polymer chains with rate-dependent crosslinkers similar to what is found in gels. The model combines the worm-like chain (WLC) at the polymer level with the transition state theory for crosslinker bond dynamics. We study the damage evolution and the force—displacement response of these networks under uniaxial stretching for different loading rates, network topology, and crosslinking density. Our results suggest a complex nonmonotonic response as the loading rate or the crosslinking density increases. We discuss this in terms of the microscopic deformation mechanisms and suggest a novel framework for increasing toughness and ductility of polymer networks using a bio-inspired sacrificial bonds and hidden length (SBHL) mechanism. This work highlights the role of local network characteristics on macroscopic mechanical observables and opens new pathways for designing tough polymer networks.

Behavior of a smart one-way micro-valve considering fluid–structure interaction

2018 ◽  
Vol 29 (20) ◽  
pp. 3960-3971 ◽  
Author(s):  
H Mazaheri ◽  
AH Namdar ◽  
A Amiri
Keyword(s):  
Interaction Effect ◽  
Fluid Structure Interaction ◽  
Pressure Head ◽  
Soft Materials ◽  
Crosslinking Density ◽  
Operational Parameters ◽  
Sensors And Actuators ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Different Temperatures

Smart hydrogels are soft materials which can be applied in sensors and actuators especially in microfluidics in which the fluid–structure interaction is important. In this work, first, the behavior of a one-way hydrogel micro-valve is investigated by considering the fluid–structure interaction effect for a specified geometry of the micro-valve. Second, both the fluid–structure interaction and non-fluid–structure interaction simulations are conducted to study the fluid flow effect on the operational parameters of the micro-valve. The obtained results show that the fluid–structure interaction effects are important and have a considerable influence on the micro-valve parameters especially on its closing temperature. Thereafter, a precise study on the micro-valve is executed by considering the micro-valve operational parameters such as inlet pressure, head size, crosslinking density, and breaking pressure at different temperatures. The results show the importance of considering the fluid–structure interaction effect in the design of these devices.

scholarly journals Mechanical properties of magnetic gels containing rod-like composite particles

2019 ◽  
Vol 377 (2143) ◽  
pp. 20180218 ◽  
Author(s):  
Mariem M. Abrougui ◽  
Modesto T. Lopez-Lopez ◽  
Juan D. G. Duran
Keyword(s):  
Mechanical Properties ◽  
Magnetic Particles ◽  
Three Dimensional ◽  
Heterogeneous Systems ◽  
Soft Materials ◽  
Polymer Chains ◽  
Composite Particles ◽  
Magnetite Particles ◽  
Magneto Rheological ◽  
Mr Effect

Magnetic gels (ferrogels) are heterogeneous systems structured at the nanoscale that contains magnetic particles dispersed in three-dimensional networks of polymer chains. In the present work, the magnetic particles were synthesized with a core–shell structure, consisting of sepiolite particles covered by magnetite nanoparticles. These composite particles had a rod-like shape with a high aspect ratio. The obtained sepiolite–magnetite particles showed a high enough susceptibility and saturation magnetization. The magneto-rheological (MR) properties, and the intensity of the MR effect, of aqueous suspensions of the synthesized particles were studied. The particles, functionalized by adsorption of alginate molecules, were imbedded in alginate hydrogels to get homogeneous soft materials. The particles were linked to the polymer chains as the knots in a network and dominated in a great extent the mechanical properties of the materials. After determining the optimal compositions of the ferrogels, their viscoelastic properties were measured in the absence/presence of magnetic fields. The results pointed out that the MR effect provided by the clay–magnetite particles was considerably more intense than those achieved in ferrogels that contain spherical magnetic microparticles. Therefore, the imbedding of rod-shaped magnetic particles in hydrogels allows controlling the mechanical properties in a wider range than in conventional ferrogels. This article is part of the theme issue ‘Heterogeneous materials: metastable and non-ergodic internal structures’.

scholarly journals Preparation and Characterization of Binary Organogels via Some Azobenzene Amino Derivatives and Different Fatty Acids: Self-Assembly and Nanostructures

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Haiying Guo ◽  
Tifeng Jiao ◽  
Xihai Shen ◽  
Qingrui Zhang ◽  
Adan Li ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Organic Solvents ◽  
Self Assembly ◽  
Alkyl Substituent ◽  
Soft Materials ◽  
Spectral Studies ◽  
Hydrophobic Force ◽  
Alkyl Chains ◽  
Morphological Studies ◽  
Amino Derivatives

In present work the gelation behaviors of binary organogels composed of azobenzene amino derivatives and fatty acids with different alkyl chains in various organic solvents were designed and investigated. Their gelation behaviors in 20 solvents were tested as new binary organic gelators. It showed that the length of alkyl substituent chains and azobenzene segment have played a crucial role in the gelation behavior of all gelator mixtures in various organic solvents. Longer alkyl chains in molecular skeletons in present gelators are favorable for the gelation of organic solvents. Morphological studies revealed that the gelator molecules self-assemble into different aggregates from lamella, wrinkle, to belt with change of solvents. Spectral studies indicated that there existed different H-bond formation and hydrophobic force, depending on different substituent chains in molecular skeletons. The present work may also give new perspectives for designing new binary organogelators and soft materials.

Process Control of Loss Factor in Soft Materials

2006 ◽  
Vol 11-12 ◽  
pp. 725-728
Author(s):  
Jun Hao Wu ◽  
Yoshitaka Ikarashi ◽  
Shuji Fujii ◽  
Seiichi Kawahara ◽  
Yoshinobu Isono
Keyword(s):  
Loss Tangent ◽  
Loss Modulus ◽  
Soft Materials ◽  
Polymer Chains ◽  
Cross Linking ◽  
Unstable State ◽  
High Loss ◽  
One Step ◽  
Deformed State ◽  
Chemical Cross Linking

Loss tangent defined by the ratio of loss modulus to storage modulus, G”/G’, is widely used as a measure of energy loss for rubber materials. We can expect high loss tangent due to unstable state of polymer chains in large deformation. However, chemical cross-linking is usually introduced in no deformation where we cannot expect high loss tangent. Even if introduced in deformed state, polymer chains take relaxation before completion of cross-linking. In this study, hence, a novel two-step cure has been proposed. The loss tangent by two-step cure has been found to be higher than that by one-step cure in no deformation, showing effectiveness of the process proposed.

scholarly journals Nanostructures and Self-Assembly of Organogels via Benzimidazole/Benzothiazole Imide Derivatives with Different Alkyl Substituent Chains

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Xihai Shen ◽  
Tifeng Jiao ◽  
Qingrui Zhang ◽  
Haiying Guo ◽  
Yaopeng Lv ◽  
...  
Keyword(s):  
Organic Solvents ◽  
Self Assembly ◽  
Bond Formation ◽  
Alkyl Substituent ◽  
Soft Materials ◽  
Molecular Structures ◽  
Spectral Studies ◽  
Hydrophobic Force ◽  
Alkyl Chains ◽  
Gelation Behavior

New benzimidazole/benzothiazole imide derivatives with different alkyl substituent chains were designed and synthesized. Their gelation behaviors in 22 solvents were tested as novel low-molecular-mass organic gelators. The test showed that the alkyl substituent chains and headgroups of benzimidazole/benzothiazole residues in gelators played a crucial role in the gelation behavior of all compounds in various organic solvents. More alkyl chains in molecular skeletons in present gelators are favorable for the gelation of organic solvents. SEM and AFM observations revealed that the gelator molecules self-assemble into different aggregates from wrinkle, lamella and belt to dot with change of solvents. Spectral studies indicated that there existed different H-bond formation between imide groups and hydrophobic force of alkyl substituent chains in molecular skeletons. The present work may give some insights into design and character of new organogelators and soft materials with special molecular structures.

scholarly journals Dynamic intermolecular interactions through hydrogen bonding of water promote heat conduction in hydrogels

2020 ◽  
Vol 7 (11) ◽  
pp. 2936-2943 ◽  
Author(s):  
Jiawei Zhou ◽  
Shaoting Lin ◽  
Hongxia Zeng ◽  
Ji Liu ◽  
Buxuan Li ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Heat Conduction ◽  
Intermolecular Interactions ◽  
Thermal Transport ◽  
Soft Materials ◽  
Intermolecular Forces ◽  
Polymer Chains

Dynamic intermolecular forces through hydrogen bonding between water and polymer chains are shown to enhance thermal transport in soft materials.

Cononsolvency Phenomena of Poly(N-Isopropylacrylamide) in Mixed Solvents at Different Temperatures

2011 ◽  
Vol 332-334 ◽  
pp. 1752-1755
Author(s):  
Xiao Xia Qiu ◽  
Jie Sun ◽  
Shu Jie Tong ◽  
Shi Jia Wang ◽  
Li Yuan Wu ◽  
...  
Keyword(s):  
Mixed Solvents ◽  
Volume Ratio ◽  
Polymer Gels ◽  
High Water ◽  
Polymer Chains ◽  
Temperature Dependent ◽  
Different Temperatures ◽  
Ft Ir ◽  
Water Fractions ◽  
Increasing Temperature

N-isopropylacrylamide was synthesized in a mixture of DMF and THF ( 7:3 in volume ratio) and characterized by FT-IR. The behavior of poly(N-isopropylacrylamide) chain was studied by spectrometer in mixtures of water with DMF and THF. Cononsolvency phenomena were found to be temperature-dependent, as demixing occurred upon increasing temperature. A significant shrinkage of polymer chains and deswelling of polymer gels, followed by phase separation, were observed for high water fractions.

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