Poly vinyl ethers n

The first synthesis of star polymers with a microgel core was reported by Sa-wamoto et al. for poly(isobutyl vinyl ether) (poly(IBVE)) [3,4]. In the first step, living cationic polymerization of IBVE was carried out with the HI/ZnI2 initiating system in toluene at -40 °C. Subsequent coupling of the living ends was performed with the various divinyl ethers 1-4. 

The effect of reaction conditions on the yield, overall molecular weight (MW) and structure of the final polymer was investigated. The studied parameters 

In addition to the effect of the experimental conditions, the influence of the nature of the arms and of the divinyl compound was also studied. It was shown that bulkiness of the arms strongly influences the yield of star polymer for instance, arms of poly(cetyl vinyl ether) were linked in very low yield as compared with poly(IBVE). The influence of the structure of the divinyl ether was investigated and appears to be of great importance. Coupling with 3 and 4 led to low yield of star polymer, while the efficiency of 1 and 2 was much higher. The explanation provided by the authors was that compact and flexible spacers between the two vinyl groups of 3 and 4 could lead to smaller cores where further reaction of incoming chains would be sterically hindered. 

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AnBn-TypeStar Copolymers Polyfvinyl ether)n-Star-Poly(vinyl ether) ... 

Cationic polymerizations are not only important commercial processes, but, in some cases, are attractive laboratory techniques for preparing well-defined polymers and copolymers. Polyacetal, poly(tetramethyl-ene glycol), poly(e-caprolactam), polyaziridine, polysiloxanes, as well as butyl rubber, poly(N-vinyl carbazol), polyindenes, and poly(vinyl ether)s are synthesized commercially by cationic polymerizations. Some of these important polymers can only be prepared cationically. Living cationic polymerizations recently have been developed in which polymers with controlled molecular weights and narrow polydispersity can be prepared. 

Because the transition state of electrophilic addition is rather open or only very weakly bridged, the stereoselectivity is poor, resulting in primarily atactic polymers. Polystyrene and most poly(vinyl ether)s prepared cationically at ambient temperature are atactic with similar proportions of meso and racemic dyads [243,244]. However, meso addition is slightly preferred with vinyl ethers, and varies from 60 to 70% for most monomers, including isobutyl, neopentyl, n-butyl, and ethoxyethyl vinyl ethers [245]. It is higher with benzyl vinyl ether (89%). This tendency to... 

A number of poly(vinyl ethers) are used in practice. Their typical structure can be described by the formula [-CH2CH(OR)-]n, the more common ones being the polymers with R = methyl, ethyl, propyl, n-butyl, or ferf-butyl. Polymers with longer radical chains such as octadecyl also are known. Poly(vinyl methyl ether) (PVME), CAS 9003-09-2, with lower DP is a viscous liquid, while the polymer with higher DP is a stiff rubber. PVME is used as a rubber plasticizer and in adhesives and paints. Poly(vinyl ethyl... 

Secondary structural variables, including the nature of the polymer backbone, will only be elucidated by synthesizing complete and homologous series of well-defined polymers. As discussed previously, only a few of the poly(vinyl ether)s, polynorbor-nenes and polymethacrylates contain both identical mesogens and spacers. These systems confirm the above trends. For example, when (4 -n-butoxyphenoxycarbo-nyl)phenoxy mesogens are attached to polymethacrylate and poly(vinyl ether) back-... 

Comparison of the phase diagrams plotted in Fig. 14 of poly(5- [ -[4 -4"-cyano-phenyl)phenoxy]alkyl]carbonyl]bicy-clo[2.2.1]hept-2-ene]s [189] and poly(n-[(4 -(4"-cyanophenyl)phenoxy)alkyl]vinyl ethers [122-127, 212, 213] which contain a single mesogen per repeat unit demonstrates that the glass transition temperature decreases as the flexibility of the polymer backbone increases from polynorbornene to poly(vinyl ether), whereas the isotropiza-tion temperature increases. In addition to revealing additional mesophases at lower temperatures, this increase in polymer flexibility enables the poly(vinyl ether)s to form more ordered mesophases. That is, poly(5- [ -[4 -(4"-cyanophenyl)phenoxy]al-kyl]carbonyl ]bicyclo[2.2.1 ]-hept-2-ene ]... 

PVA n. Poly (vinyl ether). Abbreviation for either polyvinyl alcohol or poly(vinyl acetate). 

Vinylmethyl ether (methyl vinyl ether) n. A low-boiling liquid (6°C) or gas, polymerizable to poly(vinylmethyl ether). It is also used as a modifier for alkyd resins and polystyrene (See image). 

Aoshima, S. and Kanaoka, S. (2008) Synthesis of stimuh-responsive polymers by living polymerization Poly(N-isopropylacrylamide) and poly(vinyl ether)s. Advances in Polymer Science, 210,169-208. 

Poly Isobutyl vinyl Ether n (polyvinyliosbutyl ether) Any polymer of isobutylvinyl ether. Some are liquids, others are solid and crystalline. They are used as adhesives, surface coatings, laminating agents, and filling compounds in electrical cables. 

Linear alkane solutions of 60a (n = 300, M = 3.1 x 10", Mw/Mn = 1.15) showed highly sensitive UCST-type phase separation irrespective of the solvent [222]. Interestingly, the cloud point temperature of 60a increased linearly with the number of carbon atoms in the alkane, which is in reasonable agreement with the Flory-Huggins theory. Similar phase separation occurred for poly(vinyl ether)s with various pendant groups, such as alkyl (in alcohols and esters), ester (in alcohols and toluene), and silyloxy groups (in alcohols). The combination of polymer and solvent was the decisive factor in sensitive phase separation. Nonpolar polymers underwent phase separation in polar solvent, and polar ones became thermosensitive in nonpolar media. 

Synthesis of Stimuli-Responsive Polymers by Living Polymerization Poly(N-Isopropylacrylamide) and Poly(Vinyl Ether)s... 

Eq. 10 presents an example of the synthesis of hetero-telechelic poly(vinyl ethers) via the base-stabilized living species 14. The ester-type adduct 1 is the functional initiator of choice, which is obtained from trifluoroacetic acid and a vinyl ether (8) with a pend-ant functionality X. In n-hexane solvent at temperatures from 0 to +60 C, the trifluoroacetate 15 can initiate living polymerization of... 

Reverse thermogelling polymers used to act as an effective injectable thermogel usually possess block architectures and a balanced structure of hydrophobicity and hydrophilicity. As temperature increases, the association of the polymers occurs due to increased hydrophobic interactions to show a temperature-sensitive sol-to-gel transition at a critical temperature, namely, lower critical solution temperature (LCST). Typical reverse thermogelling polymers include poly(N-substimted acrylamide)-based block copolymers [7-11], poly(vinyl ether)-based block copolymers, poly(ethylene oxide) (PEO)/poly(propylene oxide) (PPO)-based block copolymers [12-17] and PEG/polyester block copolymers [18-23], The representative structures of each class are shown in Fig. 1. In most cases, PEG was used as a hydrophilic block. All the themogelling hydrogels formed from the amphiphilic block copolymers mentioned above exhibit a sol-gel phase-transition in the physiological conditions in a tunable manner and have been intensively studied in recent years. 

N. A. Rotstein, T. P. Lodge. Tracer diffusion of linear polystyrenes in poly-(vinyl methyl ether) gels. Macromolecules 25.T 316-1325, 1992. 

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