Rheologische Untersuchungen an nebenvalenzmäßig vernetzten Gelen aus iso- und syndiotaktischem PMMA

Pyrlik, M.; Rehage, G.

doi:10.1007/bf01384032

Cited by 19 publications

(7 citation statements)

References 43 publications

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“…Formation of stereocomplexes between i-PMMA and s-PMMA was first reported by Liquori and co-workers (23). Other factors, such as the polymer concentration (47)(48)(49), mixing ratio (50-52), molecular weight (53)(54)(55), and solvent effect (56,57) of the stereoregular polymers, also affect formation of stereocomplexes between i-PMMA and s-PMMA. In addition, stereocomplexes composed of tactic PMMAs are known to be produced both in bulk and in solution (51)(52)(53).…”

Section: Complex Formation In Mixtures Of Pmma Of Opposite Tacticitiesmentioning

confidence: 85%

Tacticity in Vinyl Polymers

Woo

Chang

2011

Encyclopedia of Polymer Science and Technology

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Various issues of tacticity in vinyl polymers are discussed. First, tacticity is defined and the concepts of tactic forms in polymers as a stereoregular configuration order are introduced, and illustration schemes for common polymer tacticity are shown. Effects of tacticity in polymer structures on crystalline morphology and property are briefly discussed. Several commercially useful tactic polymers are examined, by using examples of vinyl‐type polymers such as tactic polypropylene (PP), polystyrene (PS), and poly(methyl methacrylate) (PMMA). Catalysts and synthesis routes for producing stereoregular tactic polymers are discussed mainly using PMMA as an example. Tacticity in polymers is related to differences in microstructures, morphology, crystalline polymorphism, and physical/mechanical properties. Tactic polymers possess structural order and are to crystallize. Tacticity and crystalline properties of polymers are discussed. Crystal polymorphism in some tactic polymers, such as syndiotactic polystyrene (s‐PS), is discussed in greater detail. Complex formation in mixtures of polymers of opposite tacticities, just like mixtures of polymers of opposite chiral forms, has been reported. Complex formation in mixtures of polymers of opposite (s‐ and i‐tacticity) is discussed using examples of isotactic PMMA (i‐PMMA) and syndiotactic PMMA (s‐PMMA); on the other hand, complex formation of mixtures of other tactic polymers, such as i‐PS/s‐PS or i‐PP/s‐PP, is not known. Effects of tacticity on the miscibility and phase behavior in blends of tactic polymers with other polymers are surveyed and expounded. Blends of polymers of same chemical structure but opposite tacticities are not always miscible, as exemplified in a blend of nonpolar and highly crystalline s‐PP with i‐PP, showing immiscibility with upper critical solution temperature behavior but a‐PP being miscible with s‐PP or i‐PP. In addition, phase behaviors of binary blends of two isomeric polymers are addressed. In blends with weak interactions and borderline phase homogeneity, the tacticity effect on miscibility is usually more pronounced; in contrast, the effect on the phase behavior may be minimal in systems with strong intermolecular interactions.

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Section: Complex Formation In Mixtures Of Pmma Of Opposite Tacticitiesmentioning

confidence: 85%

Tacticity in Vinyl Polymers

Woo

Chang

2011

Encyclopedia of Polymer Science and Technology

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“…The maximum of the curve increases in the course of time and shifts from i/s=1/1 to i/s=1/2. For the stereocomplexation of PMMA, a minimum sequence length is required [31][32][33][34][35][36]; for most solvents 8 to 10 monomeric units are needed. Although measurement techniques can yield quite high fractions of isotactic and syndiotactic dyads, this does not always mean that all sequence lengths are long enough.…”

Section: D) Complex Formationmentioning

confidence: 99%

On the nature of crosslinks in thermoreversible gels

2006

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SummaryA review is given concerning the nature of crosslinks in thermoreversible gels. In these gels the crosslinks can be formed e.g. by means of crystallisation of parts of polymer molecules, by liquid-liquid phase separation in solution and in bulk, by hydrogen bridging, by complexation of polymer chains, by helix formation, by chemical equilibrium reaction or by interactions between side-chains. One example will be given for each of these eight possibilities of crosslink formation.

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“…In this complex the syndiotactic PMMA chains enfold the isotactic chain by adopting a 9 1 double‐stranded helix to form a so‐called supramolecular structure consisting of one isotactic unit and two syndiotactic units. The stereocomplex is generally formed in solution, and when the polymer concentration of the solution is high a physical gel is formed by crosslinking through the stereocomplex crystallites 77. The dried residues of the solution or gel are crystalline, with a high melting point (180 °C) and properties different from those of the ordinary PMMA.…”

Section: Introductionmentioning

confidence: 99%

Stereocomplexed polylactides (Neo‐PLA) as high‐performance bio‐based polymers: their formation, properties, and application

Fukushima

Kimura

2006

Polymer International

410

316

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Polymeric materials prepared from renewable natural resources are now being accepted as ''bio-based polymers'', because they are superior to the conventional petroleum-based polymers in reducing the emission of carbon dioxide. Among them, poly(L-lactide) (PLLA) prepared by fermentation and polymerization is paid an immediate attention. Although PLLA exhibits a broad range of physico-chemical properties, its thermal and mechanical properties are somewhat poorer for use as ordinary structural materials. For improving these inferior properties, a stereocomplex form consisting of PLLA and its enantiomer poly(D-lactide) (PDLA) has high potential because of showing high melting nature (230 • C). It can be formed by simple polymer blend of PLLA and PDLA or more easily with stereoblock polylactides (sb-PLA) which are PLLA/PDLA block copolymers. These novel PLA polymers, named ''Neo-PLA'', can provide a wide range of properties that have never be attained with single PLLA. Neo-PLA retains sustainability or bio-based nature, because both monomers L-and D-lactic acids are manufactured from starch by fermentation.

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Rheologische Untersuchungen an nebenvalenzmäßig vernetzten Gelen aus iso- und syndiotaktischem PMMA

Cited by 19 publications

References 43 publications

Tacticity in Vinyl Polymers

Tacticity in Vinyl Polymers

On the nature of crosslinks in thermoreversible gels

Stereocomplexed polylactides (Neo‐PLA) as high‐performance bio‐based polymers: their formation, properties, and application

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