Cell-penetrating poly(disulfide)s: focus on substrate-initiated co-polymerization
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Outperforming cell-penetrating peptides, cell-penetrating poly(disulfide)s are attracting increasing attention. Recently we have shown that cell-penetrating poly(disulfide)s can be grown directly on substrates of free choice before delivery and depolymerized right afterwards. These unique characteristics are compatible with the general, non-toxic, traceless yet covalent delivery of substrates in an unmodified form. The objective of this study was to elaborate on substrate-initiated co-polymerization. The original propagators contain a strained disulfide for ring-opening disulfide-exchange polymerization and a guanidinium cation to assure cell-penetrating activity. Here, we report individually optimized conditions to polymerize these original propagators together with several other propagators. The nature of these new propagators significantly affected polymerization efficiency and conditions as well as size, polydispersity and transport activity of the final co-polymers. According to gel permeation chromatography, the length of co-polymers increases with hydrophobicity, bulk and valency of the co-propagators, whereas ion pairing with boronates gives shorter co-polymers and branching increases polydispersity. The activity of co-polymers increases with length, π-acidity, superhydrophobicity and boronate counterions. Hydrophobicity, π-basicity, bulk and branching appear less important for activity in fluorogenic vesicles. The here reported design, synthesis and evaluation of substrate-initiated co-polymers will be essential to find the best cell-penetrating poly(disulfide)s.Keywords:
Dispersity
The major component of a photoresist formulation is a matrix resin, which therefore has the greatest effect on resist performance. At deep-UV wavelengths the resins of choice are linear phenolic polymers, such as poly(4-hydroxystyrene) (PHOST), which have excellent absorption characteristics within the DUV region. This paper demonstrates the synthesis of a range of narrow polydispersity PHOST polymers (Mn equals 2,000 - 30,000; PD equals 1.1 - 1.4) via a 'living' radical polymerization technique. Further, the effects of polydispersity and molecular weight on the dissolution behavior and thermal properties of these polymers are reported.
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Photoresist
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Size-separation characterization techniques such as size-exclusion chromatography separate polymers by hydrodynamic volume, not molecular weight; this makes it impossible to directly obtain the true molecular weight distribution, because each elution slice at a given hydrodynamic volume contains a range of molecular weights (“local polydispersity”). Simulations are used to show that, for randomly hyperbranched polymers, this spread of molecular weights is narrow for all except very low molecular weights. To a good approximation, size-exclusion techniques give the actual molecular weight distribution for hyperbranched polymers. This applies to synthetic polymers such as polyglycerol, the natural polymer glycogen, and others.
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Abstract This recommendation defines just three terms, viz., (1) molar-mass dispersity, relative-molecular-mass dispersity, or molecular-weight dispersity; (2) degree- of-polymerization dispersity; and (3) dispersity. "Dispersity" is a new word, coined to replace the misleading, but widely used term "polydispersity index" for M w / M n and X w / X n . The document, although brief, also has a broader significance in that it seeks to put the terminology describing dispersions of distributions of properties of polymeric (and non-polymeric) materials on an unambiguous and justifiable footing.
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This recommendation defines just three terms, viz., (1) molar-mass dispersity, relative-molecular-mass dispersity, or molecular-weight dispersity; (2) degree-of-polymerization dispersity; and (3) dispersity. “Dispersity” is a new word, coined to replace the misleading, but widely used term “polydispersity index” for M¯w/M¯n and X¯w/X¯n. The document, although brief, also has a broader significance in that it seeks to put the terminology describing dispersions of distributions of properties of polymeric (and non-polymeric) materials on an unambiguous and justifiable footing.
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The e.s.r. spectrum of the 4,5-methylenephenanthrene dianion radical has been studied with particular interest in the variation of the alkali-metal splitting constant with the nature of the solvent, the nature of the counterion, and temperature. The results may be interpreted in terms of interaction of the unpaired electron with one counterion only. The results also indicate that a variety of environments are possible for the counterion in the 'contact' ion pair and that in particular cases an equilibrium is also present in which this counterion is in a 'solvent-separated' environment. Interaction of the unpaired electron with the second counterion is not observed and is probably due to a solvent separated environment for this counterion.
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Abstract This recommendation defines just three terms, viz., 1. molar‐mass dispersity, relative‐molecular‐mass dispersity, or molecular‐weight dispersity, 2. degree‐of‐polymerization dispersity, and 3. dispersity. “Dispersity” is a new word, coined to replace the misleading, but widely used term “polydispersity index” for M̄ w / M̄ n and X̄ w / X̄ n . The document, although brief, also has a broader significance in that it seeks to put the terminology describing dispersions of distributions of properties of polymeric (and non‐polymeric) materials on an unambiguous and justifiable footing. Copyright © 2009 Society of Chemical Industry
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Abstract A viscometric polydispersity index may be calculated by forming the ratio of the viscosity‐average molecular weights of a polymer in a relatively good solvent and in a relatively poor solvent and subtracting 1. This index has been examined by measuring dilute solution viscosities of a polydisperse polystyrene and a polydisperse methyl methacrylate in a variety of solvents, calculating viscosity‐average molecular weights using Mark‐Staudinger‐Houwink equations, and forming the viscometric polydispersity indices. These are compared to Schulz parameters, weight‐average–number‐average molecular weight ratios minus 1, determined from osmotic pressure and light scattering. Viscometric polydispersity indices are more sensitive to polydispersities than expected when compared to Schulz parameters if account is taken of the differences in the powers of molecular weight in the various molecular weight sums. Viscometric polydispersity indices are examined for other polymers, including an almost monodisperse polystyrene. From these measurements it is concluded that the viscometric polydispersity index is valuable for characterizing the polydispersity of polydisperse linear polymers and rough fractions. The weight‐average–viscosity‐average polydispersity index is more sensitive than the viscometric polydispersity index and may be used to characterize relatively monodisperse linear polymers.
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Polystyrene
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