Polyisoprene, PIP

Figures 7 and 8 show the original morphologies of the block copolymers observed by TEM selectively stained P4VP, P2VP, and polyisoprene (PIP) sequences...

Functionalized polysiloxanes are attractive because, with only small modification of the polysiloxane properties (e.g. density, yield strength, etc.), they allow reduction in the interfacial tension thanks to better interactions with the other homopolymer. Two studies involving PB/PDMS and polyisoprene (PIP)/PDMS are of particular interest [19,20]. The PDMS end groups were either amine (-NH2) or acid (-COOH). It was first observed that the PB/PDMS-NH2 system exhibits a 30% reduction in interfacial tension compared to the equivalent PB/PDMS system. A preliminary reduction... 

Recent studies of blends of polyisoprene (PIP) with polybutadiene (PBD) have revealed a number of remarkable features [1-5]. Non-polar hydrocarbon polymers such as PIP and PBD are not expected to exhibit miscibility given the absence of specific interactions. When the polybutadiene is high in 1,2 microstructure, however, it has a remarkable degree of miscibility with PIP. This miscibility is the consequence of a close similarity in both the polarizability and the expansivity of the two polymers [3,4]. Their mixtures represent a very unusual instance of miscibility between chemically distinct, non-reacting homopolymers. As its 1,4- content increases, both the polarizability and the thermal expansivity of the PBD diverge from that of PIP, resulting in a reduced degree of miscibility. This effect of PBD microstructure on miscibility with PIP can be seen in the data in Table I [3]. ... 

If a polymer is easily soluble in a solvent, by convention, the solvent is called a good solvent, and the converse, it is a poor solvent [6], Therefore, a solvent whose 8 value is close to the 8 value of a polymer family is a good solvent for this polymer family. As examples, the 8 value of polystyrene (PS) is about 18, which is closer to the 8 value of 18.6 of tetrahydrofuran (THF) than the 8 value of 16.8 of cyclohexane (CH). Therefore, THF is expected to be a better solvent for PS than CH. For polyisoprene (PIP), the situation is reversed CH is a better solvent than THF. 

The sulfonation of low molecular weight model olefins was undertaken to determine the feasibility of this approach. Competitive sulfonations using acetyl sulfate were carried out on the model compounds below, representing the repeat structures of cis-l,4-polyisoprene (PIP), cw-l,4-polybutadiene (c-PBD), and trans-l,4-polybutadiene (Z-PBD), respectively. It was necessary to model both the cis and trans isomeric forms of 1,4-polybutadiene, since ttey have a nearly equal probability of occurrence when the anionic polymerization (Ii counterion) is conducted in a nonpolar hydrocarbon medium... 

Polymer Preparation. Two bifunctional (telechelic) polymers were used in this study. Carboxy-telechelic polybutadiene (PB) is commercially available from B. F. Goodrich (Hycar CTB 2000X156) with molecular characteristics of Mn=4,600, Mw/Mn= 1.8, functionality 2.00 and cis/trans/vinyl ratio of 20/65/15. Carboxy-telechelic polyisoprene (PIP) was prepared by anionic polymerization in THF at -78°C with a-methylstyrene tetramer as a difunctional initiator. The living macrodianions were deactivated by anhydrous carbon dioxide. Five polymers werejjrepared with Mn=6,000 10,000, 24,000, 30,000 and 37,000 having Mw/Mn=sl.l5 a microstructure ratio of 3, 4/1, 2 of 65/35, respectively, and a functionality >1.95. 

The sensing materials used are polyisobutylene (PIB), polyepichlorohy-drin (PECH),polydimethylsiloxane (PDMS),polyisoprene (PIP), and polybutadiene (PBD) ... 

Semiconductor device arrays were examined to classify the agents at different operating temperatures. In addition, the sensing properties of an array could include different sensing membrane SAW sensors (polyisobuth-ylene (PIB), polyepichlorohydrin(PECH), polydimethysiloxane (PDMS), polybutadiene (PBD), and polyisoprene (PIP)). 

Reliable theoretical expressions for the -parameter in good solvents are not yet available. However, a semiempirical equation for gr, has been suggested by Douglas et al. [1990] based on a fit to experimental data for polystyrene (PS), polyisoprene (PIP), and polybutadiene (PBD) star polymers. The equation is... 

Core-shell morphology consisting of silica as the nano-core encapsulated by polyisoprene (PIP) was prepared as the nano-shell by a differential microemulsion polymerization of isoprene on silane treated nano-silica. PIP-Si02 nanocomposite were used as an effective nanofiller in NR latex. NR filled with PIP Si02 pre-vulcanizate clearly showed an improvement in the... 

The carboxy telechelic PBD commercialized by BF Goodrich un r trade mark ycw CTB 2000 x 156 was lai ely used in this work (M ) = 4,600 Myy/Mn = 1.8 functionality = 2.01 and microstructure cis/trans/vinyl = 20/65/15). Carboxy telechelic polyisoprene (PIP), poly a-methylstyrene (PMS) and poly tert.butylstyrene (PTBS) were prepared by anionic polymerization in THF at -78°C. 

Methods have also been developed to evaluate the average MWs by analyzing the fragments produced with SIMS from the surfaces of polymer materials. Studies conducted by Galuska on a variety of hydrocarbon elastomers (polyisoprene [PIP], polybutadiene [PBD], and PIB) and thermoplastics (polyethylene [PE], PS, polypropylene [PP], and poly(1-butene) [Pl-B]) [133] demonstrated that the relative intensity of the protonated monomer (F) can be correlated with the average MWs (M ), according to the general relationship ... 

Polyisoprene. As with polybutadiene, polyisoprene (PIP) and natural rubber are cross-linking polymers. The radical intermediates have been identified as allyl radicals (336,337,342). Radical srields at 77 K ranging from 0.28 to 0.73 have been reported. It is also clear that the mechanism of reaction of these radicals is similar to that discussed above for polybutadiene. A G-value of 6.7 for the decrease in imsaturation has been reported by Golub and Danon (347). Much later, using solid-state NMR, Whittaker (349) obtained a G(d.b.) value of 45.8 (0-1 MGy). Significantly lower yields of cross-links have been reported Boehm (350) has compiled a list of G(X) values ranging from 0.4 to 3.5 as determined by measurement of physical properties. 

Peroxyl radical reaction with the polymer. This is a generally much slower process, which is structure dependent. In saturated hydrocarbon polymers, e g. polyethylene (PE) and polypropylene (PP), it is exclusively a hydrogen atom abstraction. In this case. Per is a hydroperoxide group (POOH). The corresponding rate constant is very low = 10 -10 l.mor. s at ambient temperature (see Table 12.7). In polyenic elastomers, e g. polybutadiene (PBD) and polyisoprene (PIP), step 3 can also be an addition to double bonds. In this case. Per is a peroxide bridge (POOP). The corresponding rate constant is also very low typically = 10 -10 l.mor. s at ambient temperature for an intramolecular addition (see Table 12.7). 

Table 72.7 Propagation reactions of oxidation and corresponding value of the rate constant iki) at ambient temperature in some common hydrocarbon polymers polypropylene (PP), polyethylene (PE), polybutadiene (PBD) and polyisoprene (PIP)...

Prediction of Infinite Dilution Activity Coefficients for Polyisoprene (PIP) Systems with Two Predictive Group Contribution Models... 

In our own work [11, 35] we have studied blends of polystyrene (PS) and cis-l,4-polyisoprene (PIP), the former labelled either at random in the m-site of the benzene ring, as in Scheme 3, or at chain ends, as in Scheme 5. This pair of polymers was chosen because they are immiscible, amorphous and have widely different T, values. Thus, any significant interaction of the two should lead to... 

There are other polymers which show in addition the chain disentangling associated, with the flow transition. An example is given by ds-polyisoprene (PIP). Figure 5.19 depicts the dielectric loss e" in a three-dimensional representation of the functional dependence on frequency and temperature. Two relaxation processes show up. The one with the higher frequency again represents the a-process, the other is called the normal mode , for reasons to be seen in a moment. 

Let us return once again to the frequency- and temperature dependent measurements of the dielectric function of polyisoprene (PIP) presented in Sect. 5.3.2. As shown in Figs. 5.19 and 5.20, two relaxation processes exist. The low frequency process, the normal mode , is the one of interest here. As already mentioned, it reflects the movements of the end-to-end distance vector R of the chain. The Rouse-model enables these movements to be treated in the case of melts which are not entangled. Earlier, we learned that the motion of the end-to-end distance vector is to a large part due to the superposition of the three lowest order Rouse-modes, polarized in the x, y and z-directions. Therefore, the dielectric normal mode, when measured for samples with molecular... 

Representative diene-based polymers include natural rubber (NR), polyisoprene (PIP), PBD, styrene—butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR), which together compose a key class of polymers widely used in the rubber industry. These unsaturated polyolefins are ideal polymers for chemical modifications owing to the availability of parent materials with a diverse range of molecular weights and suitable catalytic transformations of the double bonds in the polymer chain. The chemical modifications of diene-based polymers can be catalytic or noncatalytic. The C=C bonds of diene-based polymers can be transformed to saturated C—C and C—H bonds (hydrogenation), carbonyls (hydrofbrmylation and hydrocarboxylation), epoxides (epoxidation), C—Si bonds (hydrosilylation), C—Ar bonds (hydroarylation), C—B bonds (hydroboration), and C—halogen bonds (hydrohalogenation). ... 

Figure 2 Latex hydrogenation of polyisoprene (PIP) and natural rubber (NR) in aqueous media with the water-soluble catalyst RhCls/TPPMS and phase transfer catalyst SDS.

MHz [125]. b Polyisobutylene (PIB) for different molecular masses. The independence of the molecular weight above or below the critical value is obvious. The minimum is broadened by the superposition of rotational diffusion of methyl side groups. The arrow indicates the temperature of the field-cycling data shown in Fig. 28 [33]. c Polyisoprene (PIP) for different frequencies. The minimum positions (solid line) suggest an Arrhenius law Ts=2x10 s exp(58 kJ/mol/RT) [125]. d PIP for different molecular masses... 

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