Polymerization.

Carothers, Wallace H.

doi:10.1021/cr60031a001

Cited by 345 publications

(213 citation statements)

References 52 publications

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“…INTRODUCTION At the time when Carothers and Flory elaborated the experimental and theoretical basis of ' 'Step-Growth Polymerizations'' [1][2][3][4] syntheses of macrocycles consisting of 10 or more atoms in the ring was a difficult task. Syntheses of macrocycles consisting of more than 20 atoms in the ring seemed to be almost impossible.…”

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confidence: 99%

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Cyclic polymers: Synthetic strategies and physical properties

Kricheldorf

2009

J. Polym. Sci. A Polym. Chem.

397

442

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Syntheses of cyclic polymers including cyclic homopolymers, cyclic block copolymers, sun-shaped polymers, and tadpole polymers are discussed on the basis of a differentiation between synthetic methods and synthetic strategies (e.g., polycondensation, ring-ring equilibration, or ring-expansion polymerization). Furthermore, all synthetic methods are classified as kinetically or thermodynamically controlled reactions. Characteristic properties of cyclic polymers such as smaller hydrodynamic volume, lower melt viscosities, and higher thermostabilities are compared to the properties of their linear counterparts. Furthermore, the nanophase separation of cyclic diblock copolymers is discussed.

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mentioning

confidence: 99%

“…Furthermore, Flory began for the first time to calculate probabilities of conformations and conformational changes and concluded (ref. 2…”

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confidence: 99%

Cyclic polymers: Synthetic strategies and physical properties

Kricheldorf

2009

J. Polym. Sci. A Polym. Chem.

397

442

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“…He suggested that this phenomenon is a result of linking polymer molecules into a three-dimensional network of infinitely large size. 4 Since the polymer network consists of inter-and intramolecularly connected polymer chains, the entire gel network can indeed be considered as one macroscopic molecule whose size is theoretically only limited by the dimensions of the containing vessel. 5 Starting from these early investigations, the development of new polymerization techniques and the understanding and resulting utilization of specific molecular interactions dramatically expanded the field of polymeric gels over the years.…”

Section: Polymeric Gels: From Macro To Micromentioning

confidence: 99%

“…While for a specific network-forming polymer l, C n and M r can be obtained from the literature, M c is the last key parameter to be determined in order to calculate the mesh size accordingly to equation (1). In general, this factor can be obtained from the Flory-Rehner equation: 31 (4) Here, M n is the number average molecular weight and is the specific volume of the polymer prior to crosslinking; is the solvent-polymer interaction parameter. Since this equation was originally derived for neutral divinyl crosslinked networks for which the molecular weight M n of the respective polymer is known, more complex derivations of this equation have been developed by Peppas et al in order to expand the theory to ionic gels or gels crosslinked during polymerization.…”

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Light-Sensitive Polymeric Nanoparticles Based on Photo-Cleavable Chromophores

Klinger

2013

Springer Theses

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This thesis focuses on the design, synthesis and characterization of novel photo-sensitive microgels and nanoparticles as potential materials for the loading and light-triggered release/accessibility of functional compounds. In order to realize this concept, different approaches to irradiation-dependent response mechanisms have been investigated.Novel light-cleavable divinyl functionalized monomeric crosslinkers based on o-nitrobenzyl derivatives were synthesized and used for the preparation of either PMMA or hydroxyl functionalized PHEMA microgels swellable and degradable in organic solvents. By the introduction of anionic MAA moieties into the PHEMA microgels, this concept was successfully transferred to double stimuli-responsive p(HEMA-co-MAA) hydrogel nanoparticles exhibiting a pH-dependent swelling and light-induced degradation behavior in aqueous media. This sensitivity to two orthogonal triggers is proposed to combine a pHinduced post-formation loading mechanism with a pH-and light-triggered release. In addition, a new class of enzyme-and light-sensitive PAAm microgels based on (meth-)acrylate functionalized dextrans as photo-and enzymatically degradable macromolecular crosslinkers was developed by introducing a photo-labile linker between the enzymatically degradable dextran chain and the polymerizable vinyl moieties. Here, the water solubility of the crosslinkers is assumed to enable an in situ loading approach of hydrophilic compounds.A different approach to the loading of microgels is based on photo-labile covalent microgel-drug conjugates. The first step to the realization of this concept was achieved by the development of a novel functional monomer consisting of a doxorubicin molecule covalently attached to a radically polymerizable methacrylate group via a photo-cleavable linker.Moreover, in order to enable the release of hydrophobic substances in aqueous media, hydrophobic nanoparticles consisting of a photo-resist polymer were designed to be degradable upon irradiation in water. Light-triggered conversion of the initial hydrophobic polymer into hydrophilic PMAA induced in situ particle dissolution and release of nile red.Since the introduction of a stimuli-responsive shell around a microgel is assumed to prevent leakage of embedded compounds, studies on non-stimuli-responsive shell formation around preformed microgel seed particles and the formation of microgel cores in polymeric shells were conducted to investigate potential synthetic pathways to this approach.In a last attempt, the surface of PHEMA and p(HEMA-co-MAA) microgels was functionalized with cinnamoyl groups in order to trigger the (reversible) particles interaction with each other by light-induced [2+2] cycloaddition reactions.

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“…Reduced wool probably consists of polypeptide chains containing cysteine r esidues . In the sense of Carothers' [19] defi,nition, these polypeptides are linear polymers bearing functional groups capable of reacting with each other to yield a threedimensional polymer. That is, oxidation of the reduced wool would form disulfide cross-linkages between different polypeptide chains and yield polymers of high molecular weight.…”

Section: Digestion Of Chemically Modified Wool Fibersmentioning

confidence: 99%

Nature of the resistance of wool to digestion by enzymes

Geiger¹,

Patterson²,

Mizell³

et al. 1941

J. RES. NATL. BUR. STAN.

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Wool that has neither been injured mechanically nor modified chemically is completely resistant t o attack by the proteolytic enzymes-pepsin, trypsin, chymotrypsin , and papain. When the cuticle or scale layer of the fib ers is damaged by mecha nical means, the wool becomes susceptible to attack by p epsin and chymotryp sin. Under these conditions only a small portion of the wool is digested, yet the fi bers are considerably weakened and their fibrous structure is partly destroyed.Wool in which the disulfide cross-linkages have been broken, as by r eduction, or by reduction followed by methylation, is almost completely digested by p epsin and chymotrypsin, but is attacked only slightly by trypsin . When the reduced wool is reoxidized and its sulfhydryl groups are converted t o disulfide groups, the wool regains its original sta bility. When the sulfhydryl groups of the reduced wool are converted to bis-thioether groups by the action of an aliphatic dihalide, the stability of the wool toward enzymes is greatly enhanced.

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Polymerization.

Cited by 345 publications

References 52 publications

Cyclic polymers: Synthetic strategies and physical properties

Cyclic polymers: Synthetic strategies and physical properties

Light-Sensitive Polymeric Nanoparticles Based on Photo-Cleavable Chromophores

Nature of the resistance of wool to digestion by enzymes

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