Polydimethylsiloxane/polybutadiene

Investigation of a wide range of block copolymers, consisting of various flexible (polydimethylsiloxane, polybutadiene) and rigid (polycarbonate, polysulphone, polyarylate) phases [44], shows that irrespective of the chemical nature of copolymer, content and molecular weight of blocks as well as pressure and composition of the hydrocarbon mixture, sorption, and mass transfer of alkanes take place primarily in the rubbery phase. The phenomenon of plasticization of polymers by hydrocarbons was demonstrated by baromechanical methods [7,45 8]. Figure 9.13 shows baromechanical curves for the block copolymer... 

In principle, A can be any polymer normally regarded as a hard thermoplastic, eg, polystyrene, poly(methyl methacrylate), or polypropylene, and B can be any polymer normally regarded as elastomeric, eg, polyisoprene, polybutadiene, polyisobutylene, or polydimethylsiloxane (Table 2). 

Polybutadiene-polydimethylsiloxane segmented copolymers were prepared by the reaction of epoxy-terminated PDMS and carboxy-terminated polybutadienes, in refluxing toluene under catalytic action of potassium hydroxide 243). Molecular weights of the copolymers obtained were usually in the low range. No other characterization data were available. 

Measurements have now been carried out on endlinked and randomly-linked samples of polybutadiene, polydimethylsiloxane, and randomly-linked samples of cis-polyisoprene. The results are presented here. 

The system with which we have begun our investigations is the styrene-dimethylsiloxane system. The dimethylsiloxane blocks should be considerably less compatible with polystyrene blocks than either polybutadiene or polyisoprene since the solubility parameter of dimethylsiloxane is much farther from that of polystyrene than are the solubility parameters of polybutadienes or of polyisoprenes (17), no matter what their microstructure. Furthermore, even hexamers of polystyrene and of polydimethylsiloxane are immiscible at room temperature and have an upper critical-solution temperature above 35°C (18). In addition, the microphases in this system can be observed without staining and with no ambiguity about the identity of the phases in the transmission electron microscope (TEM) silicon has a much higher atomic number than carbon or oxygen, making the polydimethylsiloxane microphases the dark phases in TEM (19,20). 

The results reported here concern highly entangled polydimethylsiloxanes (PDMSs), polybutadienes (PBs) and polyethylenes (PEs) containing no additives [3,14,15]. Their main rheological characteristics are set out in Table 1. 

Simnle polymers In particular, they must contain no filler and have no chemical reaction during flow. The results reported in this study were obteuned with polydimethylsiloxanes (PDMSs), polybutadienes (PBs) and polyethylenes, whose main rheological characteristics are shown in Table 1 [7, 8, 32]. They sure either linear or branched, melt when heated or at eunbient temperature and cover a wide range of molecular weights. 

PE, polyethylene PS, polystyrene PDMS, polydimethylsiloxane PIB, polyisobutylene PMMA, (atactic) polymethylmethacrylate l,4PBd, 1.4-polybutadiene 1,4PI, 1,4-polyisoprene. 

Hydrophobic blocks that are used for polymersome fabrication are inert polyethylethylene, polybutadiene, polystyrene, polydimethylsiloxane, degradable poly(lactic acid) (PLA), and poly(e-caprolactone) (PCL). Hydrophilic blocks include negatively charged poly(acrylic acid) and cross-linkable poly-methyloxazoline. Neutral PEG is more common for bioapplications. Among block copolymers, PEO-PLA and PEO-PCL are becoming widely adopted [26]. 

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

Hetfieljs, J. Sabata, S. Podesva, J. Netopilik, M. Latalova, P. Spevacek, J., Syntheses of Triblock Polybutadiene-Polydimethylsiloxane Copolymers by Coupling Reaction. J. Appl. Polym. Sci. 2006,101, 3233-3240. 

Ciolino, A. Villar, M. A. Valles, E. Hadjichristidis, N., Synthesis and Characterization of Model Polybutadiene-l,4-b-Polydimethylsiloxane-b-Polybutadiene-l,4 Copolymers. J. Polym. Sci., Part A Polym. Chem. 2007,45,1579-1590. 

Synthesis. Polybutadiene (PBD) and polydimethylsiloxane (PDMS) were selected as the elastomers. The synthesis of the corresponding AB and ABA block copolymers is shown in Schemes 1 and 2 respectively. The synthesis of the AB and ABA-PBD-block copolymers does not require the use of the acetal initiator 1 and could easily be carried out using simple one- and two-ended lithium initiators. However, the merit of the present synthetic method is that AB, ABA and (AB)a copolymers may be prepared from the same precursor, 12. Similar considerations apply for the PDMS-PMMA copolymers. The use of 1,1-diphenylethylene as a capping agent is needed to prevent nucleophilic attack of the reactive allylanion of living PBD on the ester group of MMA.1 The use of the masked OH initiator 1... 

The strain measures for dry (unswollen) vulcanizates of a large number of natural rubbers, butadiene-styrene and butadiene-acrylonitrile copolymers, polydimethylsiloxanes, polymethylmethacrylates, polyethylacrylates and polybutadienes with different degrees of crosslinking and measured at various temperatures re confined within the shaded area in Fig. 1. These measures were determined from the stress as a function of extension at (or near) equilibrium, i.e. by applying Eq. (7). Therefore they only reproduce the equilibrium stress-strain relation for the crossllnked rubbers. In all cases the strain dependence of the tensile force (and hence of the tensile stress) was expressed in terms of the well-known Mooney-Rivlin equation, equating the equilibrium tensile stress to ... 

Some highly entangled hnear polymers, including high-density polyethylene (HDPE), hnear low-density polyethylene (LLDPE), 1,4-polybutadiene (PBDE), and polydimethylsiloxane (PDMS), exhibit an extrusion instabihty known as sharkskin, in which a small-amplitude, high-frequency disturbance appears on the extru-date surface at a wah shear stress that is typically on the order of the hnear viscoelastic plateau modulus (0.1 - 0.2 MPa for most polymers). Figure 12.10 shows... 

Systematic smdies on the microdomain morphology of linear ABC Mblock terpolymers (hereafter called linear ABC) are limited to several systems. Linear ABC samples were predominantly synthesized by sequential living anionic polymerizations, which limit the kinds of monomers. Thus, polystyrene (PS) and polyisoprene (PI) or polybutadiene (PB) as well as their hydrogenated polymers such as poly(ethylene-a/t-propylene) (PEP) or poly(ethylene-aft-butylene) (PEB) were used as the A and B blocks, while poly(2-vinylpyridine) (P2VP), poly(4-vinylpyridine) (P4VP), poly(methyl methacrylate) (PMMA), poly(tert-buthyl methacrylate) (PtBMA), poly(ethylene oxide) (PEO) or polydimethylsiloxane (PDMS) was used as... 

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