Morphology and properties of PVC/solvent gels

Yang, Yongqing; Geil, P. H.

doi:10.1080/00222348308215202

Cited by 80 publications

(74 citation statements)

References 23 publications

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“…12 In those studies, cryofixation, cryofracturing, and freezedrying techniques have been used to examine the interior structure of hydrogels because solvent (e.g., water) inside hydrogels can be easily removed by sublimation with minimal disturbance of structure. [12][13][14] For example, Hong et al visually observed the 3-dimensional network structure of PVC/dioxane gel and the characteristic of this network structure increased with an increase in the molecular weight and concentration of PVC. 13 Similarly, Kim and Chu very recently reported the visual observation (by SEM) of a unique 3-dimensional honeycomb-like network structure in the interior of a swollen dextran-methacrylate hydrogel.…”

Section: Introductionmentioning

confidence: 95%

Pore structure analysis of swollen dextran-methacrylate hydrogels by SEM and mercury intrusion porosimetry

Kim¹,

Chu²

2000

J. Biomed. Mater. Res.

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The objectives of this study were to visually examine the surface and interior morphology of a new class of biodegradable hydrogels based on dextran-methacrylate and to quantify the porous structure of these hydrogels in swollen state. Two techniques (scanning electron microscopy and mercury intrusion porosimetry) were used to analyze pore structure of dextran-methacrylate hydrogels as a function of the degree of methacrylate substitution. SEM was used to observe 3-dimensional network structure of cryofixed and fractured swollen dextran-methacrylate hydrogels. Image analysis of the SEM data revealed different pore shapes and sizes, depending on the degree of substitution and the location within the hydrogel. A higher methacrylate-substituted dextran hydrogel showed a compact and rigid pore structure, while a lower substituted hydrogel showed a delicate and fragile pore structure. Mercury intrusion porosimetry analysis of the pore structure of dextran-methacrylate hydrogels provided useful and more reliable quantitative data of pore characteristics, such as total pore area, average pore diameter, their distribution, and bulk density. The total pore area and average pore diameter of swollen dextran-methacrylate hydrogels decreased with an increase in degree of methacrylate substitution, while bulk density increased with an increase in degree of substitution.

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Section: Introductionmentioning

confidence: 95%

Pore structure analysis of swollen dextran-methacrylate hydrogels by SEM and mercury intrusion porosimetry

Kim¹,

Chu²

2000

J. Biomed. Mater. Res.

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“…There is no published study about SEM examination of the interior three-dimensional network structure of waterbased biodegradable hydrogels such as dextran although a few researchers reported the use of a freezedry technique in studying polyvinyl chloride/solvent gels. 14,15 In this paper, we report a cryofixation technique for SEM structural characterization of swollen dextran-methacrylate hydrogel, particularly its threedimensional interior network structure.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of dextran-methacrylate hydrogels and structural study by SEM

Kim

Chu

2000

J. Biomed. Mater. Res.

151

115

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The objectives of this study were to develop a simple and reproducible method for the preparation of the hydrogel precursor dextran-methacrylate and to conduct a visual observation of the interior structure of the swollen dextran-methacrylate hydrogel with minimum artifacts. A dextran-methacrylate hydrogel precursor was synthesized by reacting dextran with methacrylic anhydride in the presence of triethylamine as a catalyst. The effects of reaction time, temperature, concentration, and catalyst amount were studied to obtain a wide range of degree of substitution (DS) in dextran by methacrylate. The dextran-methacrylate synthesized showed an enhanced solubility in water and common organic solvents. UV irradiation of dextran-methacrylate by a long-wave UV lamp (365 nm) generated a photocrosslinked hydrogel. This dextran-methacrylate hydrogel showed a range of swelling ratio from 67 to 227% and exhibited an increase in swelling ratio with a decrease in methacrylate substitution. The pH of the swelling media did not affect the swelling behavior of the dextran-methacrylate hydrogels at all the degrees of substitution used. Special cryofixation and cryofracturing techniques were used to prepare aqueous swollen dextran-methacrylate hydrogel samples for SEM observation of their surface and interior structures. A unique three-dimensional porous structure was observed in the swollen hydrogel but was absent in the unswollen hydrogel. Different pore sizes and morphologies between the surface and the interior of swollen hydrogels also were observed.

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“…It is interesting that there have been a number nothing about the size of the species accreting onto the particle of reports about nodular structures in amorphous polymers during its growth. For example, both Winnik (10) amorphous polystyrene., has not been particularly strong (16,(19)(20)(21)(22)(23). The nodules were certainly evident in similar sectioned particles examined by regular TEM (4), where interior features on the order of 50-100 nm seemed to orient in lines parallel to the sectioning knife edge.…”

Section: Discussionmentioning

confidence: 70%

Non-equilibrium particle morphology in dispersion-polymerized polystyrene particles

Paine¹,

Shivers²

1995

Can. J. Chem.

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Abstract:The interior particle morphology of dispersion-polymerized polystyrene particles was investigated by freeze fracture TEM (FFTEM) in order to compare the morphology of particles formed under two extreme mechanistic conditions: (a) particle growth by scavenging of dead polymer chains formed in solution (which gives rise to large particles of 5-10 pm) and (b) particle growth by oligomeric radical capture and polymerization inside the particle (giving rise to small particles of 1 pm or less). Although not generally recognized in the literature, ascribing mechanistic significance to an observed morphology requires a demonstration that the morphology is of the non-equilibrium type, i.e., the morphology depends upon how the particle was formed. An equilibrium morphology, by definition, must be independent of the particle formation route, and therefore cames no mechanistic information. In this case, large PS particles of 6.5 pm were found to have a nodular morphology that was unchanged on heating well above Tg, indicating an equilibrium structure (the nodularity of amorphous polymers is briefly rationalized by comparison with literature results over the past 20 years). On the other hand, small PS particles of 1.3 pm had a pronounced radial structure that could be converted into the nodular morphology by the same heat treatment, or by dissolving and precipitating from a suitable solvent combination. This means that the small particles have a non-equilibrium morphology, from which we may attempt to draw mechanistic inferences consistent with the suspected growth mechanism.Key words: dispersion-polymerized polystyrene, non-equilibrium polystyrene particle morphology, freeze fracture transmission electron microscopy.RCsumC : On a Ctudik la morphologie de la particule intkrieure d'une dispersion de particules de polystyrkne (PS) par la technique de FFTEM dans le but de comparer la morphologie des particules formkes sous deux conditions mkcanistiques extr&mes : (a) croissance des particules par pikgeage des chaines mortes de polymkre formCes en solution (qui donnent lieu & de grosses particules de 5-10 pm) et (b) croissance des particules par une capture d'un radical oligomCrique et une polymkrisation & l'inttrieur de la particule (donnant lieu 2 de petites particules de I pm ou moins). M&me si ce fait n'est gtnkralement pas reconnu dans la littkrature, l'attribution d'une signification mkcanistique i une morphologie observCe ntcessite une demonstration que la morphologie est d'un type non Cquilibrk, c'est-&-dire que la morphologie dkpend de la faqon dont la particule s'est forrnCe. Par definition, une morphologie d'equilibre doit &tre indkpendante de la voie de formation de la particule; elle n'a donc aucune signification mkcanistique. Dans ce cas, on a trouvk que de grosses particules de PS de 6,5 pm posskdent une morphologie nodulaire qui ne change pas par chauffage & des tempkratures bien supkrieures & la T,; ceci suggkre l'existence d'une structure en tquilibre (on rationalise brikvement le caractkre nodulaire d...

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Morphology and properties of PVC/solvent gels

Cited by 80 publications

References 23 publications

Pore structure analysis of swollen dextran-methacrylate hydrogels by SEM and mercury intrusion porosimetry

Pore structure analysis of swollen dextran-methacrylate hydrogels by SEM and mercury intrusion porosimetry

Synthesis and characterization of dextran-methacrylate hydrogels and structural study by SEM

Non-equilibrium particle morphology in dispersion-polymerized polystyrene particles

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