Diblock copolymers of polystyrene‐b‐poly(1,3‐cyclohexadiene) exhibiting unique three‐phase microdomain morphologies

Abstract

ABSTRACT:The synthesis and molecular characterization of a series of conformationally asymmetric polystyrene-blockpoly(1,3-cyclohexadiene) (PS-b-PCHD) diblock copolymers (PCHD: 90% 1,4 and 10% 1,2), by sequential anionic copolymerization high vacuum techniques, is reported. A wide range of volume fractions (0.27 / PS 0.91) was studied by transmission electron microscopy and small-angle X-ray scattering in order to explore in detail the microphase separation behavior of these flexible/semiflexible diblock copolymers. Unusual morphologies, consisting of PCHD core(PCHD-1,4)-shell(PCHD-1,2) cylinders in PS matrix and three-phase (PS, PCHD-1,4, PCHD-1,2) four-layer lamellae, were observed suggesting that the chain stiffness of the PCHD block and the strong dependence of the interaction parameter v on the PCHD microstructures are important factors for the formation of this unusual microphase separation behavior in PS-b-PCHD diblock copolymers. V C 2016

Role of tunable polymer flexibility in controlling wetting behavior and thermal properties of poly(1,3‐cyclohexadiene)‐silica nanocomposites

“…To extend the spectrum of flexible polymer matrices, we utilized a low and high molecular weight polystyrene (PS). The use of PS is justified for the following reasons: (i) shares a hydrocarbon six‐membered cyclic structure in the repeat unit with PCHD, (ii) polystyrene in presence of PCHD acts as a plasticizer, [ 24 ] (iii) a singlephase transition (one T g ) is observed for PS‐b‐PCHD diblock copolymers in our past studies and the self‐assembly in bulk phase is dominated by PCHDs rod‐like configuration, when PS chains are short [ 24,25 ] and PCHD mainly dictates the phase behavior by minimizing its defect‐free energy, while contribution of PS is minimal and that of a plasticizer, confirmed in the work by Misichronis et al [ 26 ] and T g values of homopolymer PS M n = 2 and 8 kDa are much lower compared with 90/10 and 70/30 chain microstructures. [ 22,24,25 ] Short polystyrene chains in the presence of PCHD can therefore be exploited as a relatively flexible matrix.…”

“…This fixes the configuration of the chain which fundamentally alters the chain stiffness resulting in higher temperature required for a thermal phase transition. [ 22,24–26 ] The 70/30 chain microstructure is, therefore, more rigid with a higher glass transition temperature for a given molecular weight of PCHD, as it is indicated by the reported T g s in Table 2. In addition to T g values, the configurational difference between the two chain microstructures have been shown to impact self‐assembly of PCHD‐based diblock copolymers in solution and blends.…”

“…In addition to T g values, the configurational difference between the two chain microstructures have been shown to impact self‐assembly of PCHD‐based diblock copolymers in solution and blends. [ 24,26 ] These past experiments demonstrate the importance of altering the configuration (chain microstructure). This avails us the opportunity to alter chain stiffness and forms the basis of our experimental investigations to discern the contribution of chain flexibility on dispersion of PGNPs.…”

“…Past studies have shown that flexibility of PCHD can be altered by varying with the ratio of 1,4 to 1,2 linkages in the chain backbone. [ 19–22,24–26 ] PCHD with chain microstructure of 70/30 is stiffer because 30% of 1,2 linkages add more kinks to the polymer backbone compared with 90/10 chain microstructure with 10% 1,2 linkages. This fixes the configuration of the chain which fundamentally alters the chain stiffness resulting in higher temperature required for a thermal phase transition.…”

Hypergolic Ignition of 1,3-Cyclodienes by Fuming Nitric Acid toward the Fast and Spontaneous Formation of Carbon Nanosheets at Ambient Conditions

“…The produced foam is considered an excellent absorbent material for oil removal, as well as a suitable thermal insulator and flame retardant. It is interesting to note that poly(1,3-cyclohexadiene), which has been synthesized via anionic polymerization method under high vacuum techniques [27][28][29][30][31], also reacts hypergolically with fuming nitric acid (Figure 11), thus expanding the usage of the method beyond monomers' reactivity [16]. It is interesting to note that poly(1,3-cyclohexadiene), which has been synthesized via anionic polymerization method under high vacuum techniques [27][28][29][30][31], also reacts hypergolically with fuming nitric acid (Figure 11), thus expanding the usage of the method beyond monomers' reactivity [16].…”