Polyisoprene, hydroxylated

Lee KM, Han CD. Order-disorder transition induced by the hydroxylation of homogeneous polystyrene-h/ock-polyisoprene copolymer. Macromolecules 2002a 35 760-769. 

Elastomers are prepared by chain extension of hydroxyl-terminated low-molecular-weight polymers followed by vulcanization 180). The most important work concerns the use of hydroxy telechelic polybutadienes and polyisoprenes in the tire industry 249 252>. The hydroxylated polydienes of molecular weight 1000-20000 are mixed with a diisocyanate, a catalyst, vulcanization agent (sulfur), and accelerator, reinforcing additives (carbon black), and surface-active agents. The reaction takes place in two steps simultaneously or consecutively ... 

According to this mechanism, natural rubber chains are expected to have one dimethylallyl terminal unit and one isoprenyl pyrophosphate terminal unit the latter may give rise to a hydroxyl group by hydrolysis. From this point of view, acyclic terpenes in the generalized structure (II) may be appropriate models for the structural characterization of natural polyisoprenes by 13C NMR spectroscopy. 

In addition to being a synthetic route to unusual graft copolymers, the metalation technique offers a way to add functional groups to the chain by reactions characteristic of organolithium compounds. Hydroxyl or carboxyl groups, for instance, can be added by treating the metalated polyisoprene or polybutadiene (22) solution with ethylene oxide or C02, respectively. The lithium alkoxide and carboxylic salt obtained (23) in... 

Unlike regular block copolymer micelles which are well permeable for reagents, triblock nanospheres with hydroxylated polyisoprene coronas, cross-linked poly(2-cinnamoyloxyethyl methacrylate) shells, and poly(acrylic acid) cores, filled with Pd nanoparticles, showed slower hydrogenation of alkenes than Pd blacks due to the need for the reactant(s) to diffuse into and the products to diffuse out of the encapsulating nanospheres [13]. On the other hand, microspheres formed by diblock poly(t-butyl acrylate)-hlocfe-poly(2-cinnamoyloxyethyl methacrylate) and filled with Pd nanoparticles demonstrated good permeability and higher catalytic activity in the hydrogenation of methyl methacrylate than the commercial Pd black catalyst [14]. 

Chloral adds to polyisoprene similarly. The reaction is catalyzed by Lewis acids [70]. Both AICI3 and BF3 are efficient catalysts. Less cross-Unking is encountered with aluminum chloride. Infra-red spectra of the products shows presence of hydroxyl groups, chlorine atoms, and vinyUdene unsaturation [70]. 

The selective hydroboration of block copolymers containing 1,2-polybutadi-ene blocks and polyisoprene poly 2-methyl-l,3-pentadine, 1,3-polybutadiene blocks, on 1,2-polybutadiene blocks have been achieved using 9-BBN as the hydroborating agent [3]. The resulting hydroborated copolymers on oxidation afford the hydroxylated copolymers having 2 glass temperature, which show the phase-separated nature of the copolymers. 

This viewpoint is supported by increase of the cohesion strength of the mbber compounds due to the modification of rubbers with polar compounds, for example, grafting of maleic anhydride to lithium polyisoprene [5] or by the treatment of SKI-3 mbber with n-nitrosodiphenylamine [6]. Modification of the Indian mbber is made similar to synthetic mbbers by pol5mier-like reactions, for example, by epoxidation [7], maleinization, hydroxylation and using some other techniques. Every of the enumerated reactions imparts a mbber some additional properties that are characteristic for the chemical properties of either functional group. The most extensive possibilities for proceeding of the chemical reactions are inherent for... 

Crystallization of cis—1,4-polyisoprene from solution at -65 C has been carried out it is therefore possible that block copolymer preparation by epoxidation, bromination or some other reaction could be accomplished with lamellas of this polymer. Lamellar crystallization of cellulose, of amylose and of polyacrylic acid have been reported substitution reactions such as acetylation or ether formation with the hydroxyl groups and esterfication of the acid groups are possible reactions to carry out with lamellas of those polymers. The use of nonaqueous systems may be better suited to prevent swelling, and therefore, attack of the crystalline regions. It should also be possible to react poly(vinylalcohol) lamellas in suspension with acids or anhydrides to form vinyl-alcohol-vinyl ester block copolymers or with phosgene to obtain chloroformate groups which can undergo further reactions. 

Kuz minskii [8] demonstrated the general features by a direct method. He observed an extensive oxidation of polyisoprene during mastication at temperatures above 80°C. He investigated also the influence of a mechanical activation on oxidation. He followed the appearance of infrared (IR) absorption bands for the carbonyl (1750-1720 cm" ) and hydroxyl groups... 

Poly(l,4-isoprene) (natural rubber) Hydroxyl-terminated natural rubber Polyisoprene vulcanizate... 

Scheme 23.3 Synthesis of perfluoroalkylated polystyrene-Z /6>cA -polyisoprene via hydroxylation followed by esterification (lyongaxetal, 1996 Wang etal, 1997 Genzeretal, 2000a, 2000b, 2000c Xiang et al, 2000 Hayakawa et al, 2000 Li et al, 2002a Hexemer et al, 2004 You et al, 2006).

Polyisoprene (PI) polymers with low Tg were used as soft segments for preparing the thermoplastic PLA related bioelastomers which were synthesized by reacting ot,co-hydroxyl polyisoprene (HO-PI-OH) with lactide using AlEts as catalyst in toluene at 90 °C as shown in Scheme 8.14. The bioelastomers actually were a kind of PLA-PI-PLA copolymer, which could be achieved in larger quantities and at higher reaction concentrations after using aluminium... 

Scheme 8.14 Synthesis of the thermoplastic PLA-related bioelastomers from ,< -hydroxyl polyisoprene and lactides.

In 1972, Minoura [188] described the asymmetric hydroboration of diene polymers more exactly, of cis- and trans-polyisoprene using triisopinocamphenyldiborane (TIDE). The hydroxylated polymers obtained after hydrolysis, (% OH max. 85 to 100) were optically active they fit the simple Drude equation. 

A nearly monodisperse PI-14-5CN was synthesized using anionic polymerization by grafting a liquid-crystalline monomer, 6-[(4-cyano-4 -biphenyl)oxy]hexanoic acid (5CN-COOH), onto a nearly monodisperse hydroxylated polyisoprene (PI). This polymer undergoes glass transition at 45 °C and N-I transition at 102 °C. 

Lee and Han (2003b) investigated linear dynamic viscoelastic properties of organoclay nanocomposites based on both SI diblock copolymer and SIOH diblock copolymer. An SIOH diblock copolymer (referred to as SI-14/3-OH) was obtained by hydroxylation of the polyisoprene (PI) block of a highly asymmetric SI diblock copolymer (SI-14/3, with Af = 1.7 x 10" and = 1.08). SI-14/3 was a... 

Figure 11.16 Force curves measured in normal methyl-terminated polyisoprene (PI, Mw=3.4kDa) and hydroxyl-terminated polyisoprene (PI-OH, Mw = 3.4kDa). The experiments were carried out with an atomic...

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