Homopolymer chains phase behavior

A considerable amount of work has focused on the design and synthesis of macromolecules for use as emulsifiers for lipophilic materials and as polymeric stabilizers for the colloidal dispersion of lipophilic, hydrocarbon polymers in compressed CO2. It has been shown that fluorinated acrylate homopolymers, such as PFOA, are effective amphiphiles as they possess a lipophilic acrylate-like backbone and C02-philic, fluorinated side chains, as indicated in Figure 4.5-1 [100]. Furthermore, it has been demonstrated that a homopolymer which is physically adsorbed to the surface of a polymer colloid precludes coagulation due to the presence of loops and tails [110]. These fluorinated acrylate homopolymers can be synthesized homogeneously in CO2 as described in an earlier section. The solution properties [111,112] and phase behavior [45] of PFOA in SCCO2 have been thoroughly examined. Additionally, the backbone of these materials can be made more lipophilic in nature by incorporating other monomers to make random copolymers [34]. 

P8 M is not the only polymer forming the isotropic smectic phase. To date, we have observed formation of that phase for a half-dozen chiral polymethacrylates and polysiloxanes. Table 5.1 summarizes the chemical structure and phase behavior of synthesized side-chain homopolymers, which carry chirally substituted side chains derived from asymmetric esters of terephthalic acid and hydroquinone. Such a structure with alternating orientation of carboxylic link groups seems to favour the formation of the IsoSm phase, whereas isomeric derivatives of p-hydroxybenzoic acid, where all carboxylic links have the same orientation, form only conventional Sm A and Sm C phases. Molar mass of all the synthesized homo- and copoly(meth)acrylates is within the range of 1 to 2-10 g mol the poiysilox-anes have the average degree of polymerization, p 35. 

He X, Zhang H, Yan D, Wang X. 2003. Synthesis of side chain liquid crystalline homopolymers and triblock copolymers with p methoxyazobenzene moieties and poly(ethylene glycol) as coil segments by atom transfer radical polymer zation and their thermotropic phase behavior. J Polym Sci Part A Polym Chem 41 2854 2864. 

As fluorinated poly(alkylacrylates) have proved to be highly soluble in compressed CO2, they present themselves as possible components in the stabilization of heterogeneous reaction systems in CO2. Indeed, there has been considerable effort in the development and synthesis of polymeric emulsifiers for lipophilic materials and stabilizers for hydrocarbon polymer dispersions in CO2. DeSimone and coworkers demonstrated the feasibility of using fluorinated alkyl acrylate homopolymers, such as PFOA, as efficient amphiphiles, owing to the lipophilic acrylate backbone and the C02-philic fluorinated pendant chains [35, 36]. As was described earlier, these fluorinated alkyl acrylates are readily synthesized homogeneously in CO2. The solution properties and phase behavior of PFOA in compressed CO2 have been thoroughly examined and reported elsewhere [37-39]. 

A—B diblock copolymers adsorb spontaneously at the interface between two immiscible A and B homopolymers. Our objective here is to make quantitative predictions of the nature of the adsorbed layer, fri this case, the phase behavior depends on (Mily one x parameter, that between the A and B homopolymers, and the statistical segment lengths of the A and B chains. The specific example that we will smdy is the adsorption of a SPB(89)-SPB(63) diblock copolymer at the interface between SPB(89) and SPB(63) homopolymers at room temperamre [A = SPB(89) and B = SPB(63)]. For this system, x = 0.0064 (system 33 in Table 19.1), I A = 0.49 nm, and /b = 0.75 nm. We consider the interface between SPB(89) and SPB(63) homopolymers with Na = 4,230 and Nr =3,600. It is straightforward to show that the two homopolymeis are highly immiscible because xAave =6.2 which is much greater than 2 (see Eq. (19.8) for definition of Nave)- We consider the adsorption of a SPB(89)-SPB(63) diblock copolymer with NAb = 790 and Nsb = 730 where the subscript b refers to the chains comprising the block copolymer. We consider two flat homopolymer-rich phases with the diblock copolymer adsorbed at the interface. The z-axis of our coordinate frame is perpendicular to the interface. The results of SCFT predictions for 0 e volume fraction of the A-B... 

Acrylic latices, phase behavior, 7,l(y Adsorbed chains on flat surfaces, 23 Adsorbing homopolymer, rheology effect, 8 Adsorption... 

Similar to the synthetic process of macromonomer polystyrene homopolymer, we have also synthesized Seesaw-type macromonomer triblock copolymer [1]. This is because we have been interested in the phase behaviors of long linear multiblock copolymer chains in selective solvents for many years [18, 19]. Therefore, we intentionally prepared Seesaw-type macromonomer triblock copolymers to construct hyperbranched block copolymers and study their solution properties. 

Over the past several years there has been significant effort in studying the subtle differences between a polymer chain in a homopolymer melt compared to a blend. Small changes in the structure of the polymer chain in the blend lead to major changes in the thermodynamic properties and phase behavior of the blend. Comparing PRISM results to MD simulations has proven to be a useful first approach towards quantifying the effects that assumptions in PRISM theory have on the local blend structure, and thus the bulk properties of polymer blends. 

In what follows, we use simple mean-field theories to predict polymer phase diagrams and then use numerical simulations to study the kinetics of polymer crystallization behaviors and the morphologies of the resulting polymer crystals. More specifically, in the molecular driving forces for the crystallization of statistical copolymers, the distinction of comonomer sequences from monomer sequences can be represented by the absence (presence) of parallel attractions. We also devote considerable attention to the study of the free-energy landscape of single-chain homopolymer crystallites. For readers interested in the computational techniques that we used, we provide a detailed description in the Appendix. ... 

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