Properties of low molecular weight block copolymers. 1. Differential scanning calorimetry of styrene-dimethylsiloxane diblock copolymers

Abstract

of and find that for 1200 EW polymer R = 1.4 ± 0.2 nm (22) for -1 < KJKg < 0. This value is in agreement with the value of 1.2-1.3 nm deduced from water transport experiments.2 The change in free energy that results from the formation of the channel is only -11 J/cm3; thus our elastic theory suggests the channels are continually forming and unforming at ambient temperatures. This is consistent with the previously proposed cluster-network model. V. ConclusionWe have derived a semiphenomenological expression for the diameter of ionic clusters in ionomers and demonstrated that this expression correctly describes the variation in cluster diameter in one perfluorinated ionomer with water content, equivalent weight, and cation form. We find the cluster diameter is dominated by a balance between hydrophilic surface interactions with the ion exchange sites and the energy of elastic deformation. The model also predicts that short channels connecting adjacent clusters are thermodynamically stable, in support of the clusternetwork model proposed by us earlier. The current elastic theory should generally apply to other ionomers, including hydrocarbon analogues and a comparison of the phenomenological parameters Kt and Kl for various ionomers should be instructive and interesting. References and Notes(1) Gierke, T.

Synthesis of POSS-containing fluorosilicone block copolymers via RAFT polymerization for application as non-wetting coating materials

“…It should be noted that T g1 of PDMS was not obvious in S1, which was presumably due to the relatively lower PDMS content in the copolymer S1 and the relatively restricted movement of the PAPOSS blocks. Similar results have been previously reported that the detection of T g1 in the DSC curves was related to the content of PDMS in the block copolymers [28,29]. Apart from S1, the T g3 values of POSS in S2 and S3 were 84.4 • C and 82.4 • C, respectively, with each about 20 • C higher than that of S1.…”

Probing the interfacial region of microphase-separated block copolymers by differential scanning calorimetry

“…2, below T g B ) are relatively straight, confirming that baseline drift is not the cause of the curvature below T g S . Complications caused by the broad DSC interphase-related curvature were faced in the work of Krause et al 12,19,20 on several styrenic block copolymers. Their data were employed to assess ⌬T g S and other thermal parameters by the intersecting-tangent second-approximation method.…”

Novel synthesis of triblock PDMS-PS-PDMS copolymers

“…This has been reported previously for PS-PDMS copolymers and is thought to be due to a change in the morphology from being microphase separated up to the T g,PS to a partially crystalline material. 2,3 This phenomenon was not observed for mixtures of the homopolymers PDMS and PS. 3 Electron micrograph films of PDMS-PS-PDMS triblock copolymer IV-A, whose composition was ϳ50% PS to ϳ 50% PDMS (M n ϳ 100kDa; GPC) show the formation of spherically shaped, dark PDMS microdomains embedded in a PS matrix (Fig.…”

“…Specifically, the electrontransfer anionic polymerization of styrene yielded telechelic PS with active anions at both ends. The addition of D 4 or D 3 to this resulted in the desired PDMS-PS-PDMS triblock copolymer. Experimentally, living anionic polymerization requires extreme care to eliminate any traces of oxygen or moisture.…”

“…1 Copolymers made up of PDMS and polystyrene (PS) blocks have been prepared. Their thermoplastic elastomeric properties, 2,3 periodic phase-separated morphologies, 2,4 and potential resistance to oxygen-reactive ion etching have been studied. 5 PS-PDMS block copolymers have been synthesized by a number of different methods.…”