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A series of poly(vinylphenol-b-vinylpyridine) (PVPh-b-P4VP) block copolymers were prepared through anionic polymerizations of 4-tert-butoxystyrene with 4-vinylpyridine followed by subsequent selective hydrolysis of the 4-tert-butoxystyrene protective groups. Infrared spectrum analysis suggests that this block copolymer possesses strong hydrogen-bonding interaction between the hydroxyl group of PVPh and the pyridine group of P4VP. DSC analyses indicate that these PVPh-b-P4VP copolymers always have higher glass transition temperatures than the corresponding PVPh/P4VP miscible blends obtained from DMF solution. However, the thermal behavior of PVPh-b-P4VP diblock copolymer shows a similar Tg value with the PVPh/P4VP blend complex obtained from methanol solution at a 1:1 (PVPh:P4VP) molar ratio. We proposed that the polymer chain behavior of the PVPh/P4VP blend from DMF solution is separated coils. However, by increasing the hydrogen bonding for PVPh-b-P4VP diblock copolymer, a polymer complex aggregate is proposed, which is similar to the PVPh/ P4VP blend complex from methanol solution. The spin-lattice relaxation time in the rotating frame ( T 1F H ) based on solid-state NMR analysis is able to provide positive evidence that the polymer complex aggregate in the diblock copolymer has a shorter T1F H value than the separated coils in the miscible blend.

We have synthesized a series of block copolymers of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene (PPO-b-PS copolymer) by atom transfer radical polymerization. The PS content in these copolymer systems was determined by using infrared spectroscopy, thermal gravimetric analysis, and solution and solid-state NMR spectroscopy; good correlations exist between these characterization methods. DSC analyses indicated that the PPO-b-PS copolymers have higher glass transition temperatures than do their corresponding PPO/PS blends. Our FTIR and solid-state NMR spectroscopic analyses suggest that the PPO-b-PS copolymers possess stronger specific interactions that are responsible for the observed relatively higher values of Tg. We found one single dynamic relaxation from the dynamic mechanical analysis, which implies dynamic homogeneity exists in the PPO-b-PS copolymer; this result is consistent with the one single proton spin‐lattice relaxation time observed in the rotating frame [T1r(H)] during solid state NMR spectroscopic analysis. In addition, the 2D FTIR spectroscopy reveals evidence for the stronger interactions between segments of PPO and PS through the formation of p-cation complexes. q 2005 Elsevier Ltd. All rights reserved.

A nanoporous polyhedral oligomeric silisesquioxane (POSS) containing eight epoxy functional groups [octakis(dimethylsiloxypropylglycidyl ether)silsesquioxane, OG] reacts with meta-phenylenediamine (mPDA) to form epoxy resin network with nanostructures. The glass transition temperature (Tg) of the cured OG/mPDA product is significantly higher than that of the diglycidyl ether of bisphenol A (DGEBA) cured with mPDA (DGEBA/mPDA) material due to the presence of the POSS cages that is able to effectively hinder the motion of the network junctions. The cured OG/mPDA product inherently possesses higher thermal stability than the cured DGEBA/mPDA product based on higher maximum decomposition rate temperature, and higher char yield of the former. However, the existence of large fraction of the unreacted amine groups causes lower initial decomposition temperature of the OG/mPDA because it tends to decompose or volatilize on heating at relatively low temperature. The dielectric constant of the OG/mPDA material (2.31) is substantially lower than that of the DGEBA/mPDA (3.51) as a consequence the presence of nanoporous POSS cubes in the epoxy matrix.