Nucleation effects of high molecular weight polymer additives on low molecular weight gels

Alexander, Symone; Korley, LaShanda T. J.

doi:10.1038/s41428-018-0076-0

Cited by 4 publications

(10 citation statements)

References 51 publications

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“…CP xerogels did not display any thermal transitions in the experimental temperature range, so it is likely that the secondary endotherms were caused by interactions between PVAc and the CP fiber assembly. The increase in transition temperature from CP40 to CP60 is due to the higher concentration of CP in the composite, which was also observed in our previous work . The concentration of CP in the composite is proportional to the number of self-assembled fiber networks that are formed, meaning that higher concentrations require more energy for dissociation.…”

Section: Resultssupporting

confidence: 84%

“…This fabrication procedure may cause gel assembly to align along the path of the spreading solution, which applies a shear force as the fiber network forms . However, this behavior was observed in samples taken from gels that were formed in vials, so this feature is more likely a characteristic of the mode and/or rate of assembly. Thus, it is concluded that the CP fiber network is templated along the high MW PVAc chains in solution via non-covalent interactions, which has been demonstrated in other MG–polymer systems. , In all cases, the transient network characteristics are preserved in the P-CP composites, independent of fabrication conditions.…”

Section: Resultsmentioning

confidence: 99%

“…In this work, we are interested in the effects of the assembly or fabrication process on the polymer matrix, so the first heating cycle provides key information on the relaxation behavior of our composites. In our previous work, we showed that anisole is a poor solvent for the EO–EPI matrix, resulting in collapsed chain conformations in solution . Due to the rapid gelation of CP molecules, EO–EPI chains are trapped in this energetically unfavorable conformation in the composite during fabrication.…”

Section: Resultsmentioning

confidence: 99%

“…In our recent work, we examined the effects of highmolecular-weight polymer additives on the nucleation of lowmolecular-weight gels. 7 Poly(ethylene oxide-co-epichlorohydrin) (EO−EPI) and poly(vinyl acetate) (PVAc) were utilized as model polymers for a collapsed chain conformation (poor solubility in gelation solvent) and an extended chain conformation (good solubility in gelation solvent), respectively. A cholesterol−pyridine (CP) molecular gel in a single solvent (anisole) served as the control molecular gel network.…”

Section: ■ Introductionmentioning

confidence: 99%

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Restricting Molecular Mobility in Polymer Nanocomposites with Self-Assembling Low-Molecular-Weight Gel Additives

Alexander

Korley

2018

ACS Appl. Mater. Interfaces

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Multiscale investigation of molecular gel additives in polymer matrices guides understanding of how solution-state assemblies result in mechanically enhanced, solid-state nanocomposites. Model polymers, poly(ethylene oxide-co-epichlorohydrin) (EO–EPI) and poly(vinyl acetate) (PVAc), were utilized as matrices and reinforced by cholesterol–pyridine (CP) nanofiber networks. The CP nanofillers suppress ethylene oxide segment melting for EO–EPI composites, whereas for PVAc nanocomposites, cause a polymer–gel dissociation transition. Incorporation of crystalline CP fiber networks led to an order of magnitude increase in tensile storage modulus due to restrictions on polymer chain mobility. This decrease in molecular mobility was confirmed by decreased loss moduli for both EO–EPI and PVAc composites. Excitingly, PVAc nanocomposites display an additional relaxation mode caused by release of PVAc chains from the transient molecular gel assembly. For both EO–EPI and PVAc composites, bulk flow can be suppressed to temperatures up to 100 °C by simply increasing the CP concentration.

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Section: Resultssupporting

confidence: 84%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Restricting Molecular Mobility in Polymer Nanocomposites with Self-Assembling Low-Molecular-Weight Gel Additives

Alexander

Korley

2018

ACS Appl. Mater. Interfaces

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“…LMWGs are formed by the immobilization of the solvent molecules in the three-dimensional (3-D) network of the gelator, which are stabilized by various noncovalent interactions [1,2,3,4,5,6,7,8,9], such as hydrogen bonding, van der Waals interactions, π−π stacking, etc. The gelation properties of LMWGs depend on various factors such as concentration [17,18], sonication [19,20,21], additives [22], and seeding [21,23]. The understanding and prediction of the gel structure and self-assembly process of LMWGs to control or tune the gelation properties are difficult because of the dynamic nature of noncovalent interactions [1,2,3,4,5,6,7,8,9,10].…”

Section: Introductionmentioning

confidence: 99%

Tuning Gel State Properties of Supramolecular Gels by Functional Group Modification

2019

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The factors affecting the self-assembly process in low molecular weight gelators (LMWGs) were investigated by tuning the gelation properties of a well-known gelator N-(4-pyridyl)isonicotinamide (4PINA). The N―H∙∙∙N interactions responsible for gel formation in 4PINA were disrupted by altering the functional groups of 4PINA, which was achieved by modifying pyridyl moieties of the gelator to pyridyl N-oxides. We synthesized two mono-N-oxides (INO and PNO) and a di-N-oxide (diNO) and the gelation studies revealed selective gelation of diNO in water, but the two mono-N-oxides formed crystals. The mechanical strength and thermal stabilities of the gelators were evaluated by rheology and transition temperature (Tgel) experiments, respectively, and the analysis of the gel strength indicated that diNO formed weak gels compared to 4PINA. The SEM image of diNO xerogels showed fibrous microcrystalline networks compared to the efficient fibrous morphology in 4PINA. Single-crystal X-ray analysis of diNO gelator revealed that a hydrogen-bonded dimer interacts with adjacent dimers via C―H∙∙∙O interactions. The non-gelator with similar dimers interacted via C―H∙∙∙N interaction, which indicates the importance of specific non-bonding interactions in the formation of the gel network. The solvated forms of mono-N-oxides support the fact that these compounds prefer crystalline state rather than gelation due to the increased hydrophilic interactions. The reduced gelation ability (minimum gel concentration (MGC)) and thermal strength of diNO may be attributed to the weak intermolecular C―H∙∙∙O interaction compared to the strong and unidirectional N―H∙∙∙N interactions in 4PINA.

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Freeze–thaw hydrogel fabrication method: basic principles, synthesis parameters, properties, and biomedical applications

Waresindo

Luthfianti

Priyanto

et al. 2023

Mater. Res. Express

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Hydrogel is being broadly studied due to their tremendous properties, such as swelling ability and biocompatibility. Numerous review articles have discussed hydrogel polymer types, hydrogel synthesis methods, hydrogel properties, and hydrogel applications. Hydrogel can be synthesized by physical and chemical cross-linking methods. One type of the physical cross-linking method is freeze-thaw (F–T), which works based on the crystallization process of the precursor solution to form a physical cross-link. To date, there has been no review paper which discusses the F–T technique specifically and comprehensively. Most of the previous review articles that exposed the hydrogel synthesis method usually mentioned the F–T process as a small part of the physical cross-linking method. This review attempts to discuss the F–T hydrogel specifically and comprehensively. In more detail, this review covers the basic principles of hydrogel formation in an F–T way, the parameters that influence hydrogel formation, the properties of the hydrogel, and its application in the biomedical field.

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Nucleation effects of high molecular weight polymer additives on low molecular weight gels

Cited by 4 publications

References 51 publications

Restricting Molecular Mobility in Polymer Nanocomposites with Self-Assembling Low-Molecular-Weight Gel Additives

Restricting Molecular Mobility in Polymer Nanocomposites with Self-Assembling Low-Molecular-Weight Gel Additives

Tuning Gel State Properties of Supramolecular Gels by Functional Group Modification

Freeze–thaw hydrogel fabrication method: basic principles, synthesis parameters, properties, and biomedical applications

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