Comb polymers

Suspensions stabilized by comb polymers may serve as colloid-based inks for fabricating three-dimensional structures. 

In such applications, the improved dispersion of nanoparticles that is yielded by comb polymers has proven to be advantageous (13,14). 

Such inks enable the production of three-dimensional structures with feature sizes as small as 100 pm (15). 

Preferred comb polymers contain two types of side chains and are water-soluble. The first type of the side chain has moieties that ionize at the pH of the coUoidal suspension. The second type of side chain is nonionizable. Comb polymers from poly(acrylic acid) and poly(ethylene oxide) have nonionizable side chains, in addition to ionizable side chains (16). 

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Anotlier model system consists of polymetliylmetliacrylate (PMMA) latex, stabilized in organic solvents by a comb polymer, consisting of a PMMA backbone witli poly-12-hydroxystearic acid (PHSA) chains attached to it [10]. The PHSA chains fonn a steric stabilization layer at tire surface (see section C2.6.4). Such particles can approach tire hard-sphere model very well [111. 

Combined cycles Combined reforming Combing Comb polymers Combustion... 

Fig. 8. General structures of polymeric dispersants (a) liomopolymer, (b) random copolymer, (c) diblock copolymer, and (d) comb polymer, where A = anchor group, B = soluble repeat unit, and C = repeat unit with solubility different from B. The repeat units may occur in sequences hundreds of...

Comb Polymers with Chromophores on the Side-Chain... 

Electron-Deficient Polymers - Luminescent Transport Layers 16 Other Electron-Deficient PPV Derivatives 19 Electron-Deficient Aromatic Systems 19 Full Color Displays - The Search for Blue Emitters 21 Isolated Chromophores - Towards Blue Emission 21 Comb Polymers with Chromophores on the Side-Chain 22 Chiral PPV - Polarized Emission 23 Poly(thienylene vinylene)s —... 

The choice of the alcohol permits manipulation of the structure of the polymer. Water and monohydric alcohols afford linear chains with carboxylic acid and ester end groups, respectively. Polyhydroxy initiators afford a route to ester end-blocked star and comb polymers (Fig. 4) (47). 

For star polymers a value of e = 0.5 has been obtained (1, V7) and studies (18) of model comb polymers indicate a value of 1.5. Other work (191 has suggested that e is near 0.5 at low LCB frequencies. For a random LCB conformation of higher branching frequency an e value between 0.7 and 1.3 might be expected, i.e. somewhere between a star and a comb configuration. 

Dendronized polymers are a subclass of comb polymers [7]. The synthetic access to comb polymers with dendrons in the side chain is somewhat more difficult and time consuming compared to most other polymers of this class. It is therefore not too far fetched to ask whether the exciting properties described above... 

Comb polymers consist of a backbone and several branches [9]. Backbone and branches are usually recognized from the synthetic procedure. The branching functionality is usually limited to 3 or 4. The backbone and/or the branches can be monodisperse. In a regular comb polymer the number of branch points per backbone is constant and the branches are equidistantly spaced along the... 

If the multifunctional coupling agent is a linear polymer, a comb polymer is... 

Functional comb polymers can be prepared by several techniques, e.g. by polymerization or copolymerization of functional macromonomers. The functional groups can be placed on side-chain extremities or distributed along the side chains. Also the backbone chain can carry functional groups. Functional combs are used as modifiers of surface activity. 

Deepak VD, Asha SK (2009) Photophysical investigation into the self-organization in pyrene-based urethane methacrylate comb polymer. J Phys Chem B 113 11887-97... 

Fig. 1. a Star polymer, b Comb polymer, c Brush, d Miktoarm star copolymer, e Star copolymer, f Star chain center-adsorbed in a plane, g Dendrimer... 

Gauger and Pakula [191] performed an MC simulation of comb polymers on the fee lattice in dilute and dense media, using the cooperative motion algorithm. It is shown that, unlike linear chains, the EV screening does not appear in the global mean size dependence on N. However, this screening is complete for the branches in the melt, which exhibit ideal behavior. 

Fig. 27. Molar mass dependence of [rj] for a fractionated comb macromolecule. The fractionation was made with a SEC/LALLS/VISC set-up. The comb macromolecule consists oi a polyimidazole backbone prepared by free radical polymerization. The imidazol side groups acted in a melt with phenylglycidylether and phthalic anhydride as multifunctional initiator for the anionic growth of polyester chains. The straight lines correspond to the behavior of unattached polyester chains and the comb polymers at low and high molar masses respectively [136]...

The recognition of the two fundamental mechanisms of reptation and arm fluctuation for linear and branched entangled polymers respectively allows theoretical treatment of the hnear rheology and dynamics of more complex polymers. The essential tool is the renormahsation of the dynamics on a hierarchy of timescales, as for the case of star polymers. It is important to stress that experimental checks on well-controlled architectures of higher complexity are still very few due to the difficulty of synthesis, but the case of comb-polymers is an example where good data exists [7]. 

Fig. 11. The schematic structure of a comb polymer q arms of molecular weight are attached with regular spacing to a backbone of molecular weight...

The simplest case of comb polymer is the H-shaped structure in which two side arms of equal length are grafted onto each end of a linear cross-bar [6]. In this case the backbones may reptate, but the reptation time is proportional to the square of Mj, rather than the cube, because the drag is dominated by the dumb-bell-like frictional branch points at the chain ends [45,46]. In this case the dependence on is not a signature of Rouse motion - the relaxation spectrum itself exhibits a characteristic reptation form. The dynamic structure factor would also point to entangled rather than free motion. 

Amorphous comb polymers, with short-chain polyethers attached to a polyphosphazene backbone (Blonsky, Shriver, Austin and Allcock, 1984), Fig. 5.15, or a polysiloxane backbone (Xia, Soltz and Smid, 1984), Fig. 5.16, have been found to be excellent hosts for alkali metal salts. The PN... 

Linear star/ Multi - Armed Comb Polymers Networks (H y per) Bra n ched... 

Star and miktostar polymers have been synthesized by living cationic polymerization using dienes and trienes as coupling agents and/or multifunctional initiators [Faust and Shaffer, 1997 Hadjichristidis, et al., 1999 Hadjikyriacou and Faust, 2000 Kennedy and Jacob, 1998 Puskas et al., 2001 Sawamoto, 1991]. Multifunctional halides such as hexaiodo-methylmelamines have also been used to obtain star and comb polymers [Ryu and Hirao, 2001 Zhang and Goethals, 2001], Hyperbranched and dendritic polymers have also been studied. 

Although not extensively studied, various architectures such as star and comb polymers have also been synthesized [Bielawski et al., 2000 Goethals et al., 2000]. 

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