PS/PVP

The main results of this miero-mechanical model in the quasi-static regime have been compared with experimental results obtained by placing polystyrene (PS)-polyvinyl pyridine (PVP) diblock copolymers with a short PVP block between PS and PVP homopolymers. The fracture toughness was found to increase linearly with E from that of the bare PS/PVP interface, while the slope of the line increased with the degree of polymerization of the block being pulled out. If the data for the different copolymers were plotted as AG vs. (where... 

Fig. 4. The effect of chain pull-out of PVP on for three PS-PVP diblocks whose PVP block varied from degree of polymerisation 49 to 220 [4].

Fig. 7. Variation of Gc with E for both PS-PMMA diblocks between PPE and PMMA ( ) and PS-PVP diblocks between PS and PVP ( ) [13]. The solid line is a fit to Eq. 8 and the dashed line to Eq. 7.

When dealing with polymer blends or blockcopolymers, surface enrichment or microstructures may be observed as already discussed in Sect. 3.1. Quite similar effects may be expected for buried interfaces e.g. between polymer and substrate where one component may be preferentially enriched. In a system of PS, PVP and diblock copolymer PS-6-PVP it has been shown by FRS that the copolymer enrichment is strongly concentration dependent [158]. In a mixed film of PS(D) and end-functionalized PS on a silicon wafer the end-functionalized chains will be attached to the silicon interface and can be detected by NR [159],... 

Fig. 15 TEM images of methanol extracted samples of PS-PVP Zn(DBS)2. A unstained and B stained with L- Reproduced from [61]...

Fig. 16 Preparation of nanoporous membranes from PS-PVP HABA block copolymer composites. Reproduced from [62]...

Fig. 1 Chemical structures of the polymers commonly used for preparation of beads poly (styrene-co-maleic acid) (=PS-MA) poly(methyl methacrylate-co-methacrylic acid) (=PMMA-MA) poly(acrylonitrile-co-acrylic acid) (=PAN-AA) polyvinylchloride (=PVC) polysulfone (=PSulf) ethylcellulose (=EC) cellulose acetate (=CAc) polyacrylamide (=PAAm) poly(sty-rene-Wocfc-vinylpyrrolidone) (=PS-PVP) and Organically modified silica (=Ormosil). PS-MA is commercially available as an anhydride and negative charges on the bead surface are generated during preparation of the beads...

Fig. 2.10 (a) TEM for an /PS = 0.35, /Vn = 203 PS-PVP diblock obtained after annealing at 140 °C for more than 6h, The PVP-rich region appears dark, (b) SANS patterns from a presheared specimen under the same conditions (Schulz et al. 1996). 

Fig. Z24 (a) TEM image from a PS-PVP diblock with /PS = 0.65 and N = 196 after disordering, quenching and annealing at 140 °C for 18 h (Schulz et al. 1996). The dark-stained region corresponds to PVP. (b) Two-dimensional SANS pattern from a presheared sample of the same diblock in the same phase.

Fig. 2.48 Self-diffusion of nearly symmetric diblock copolymers measured using forced Rayleigh scattering (Dalvi et al. 1993). (a) Diffusivities, D, for the lower molecular weight PS-PVP sample, which is disordered at these temperatures, have been scaled down by a factor of 0.48, assumming Rouse dynamics (b) D for the lower molecular weight symmetric PEP-PEE diblock copolymer have been scaled down by a factor of 0.40, assuming reptation dynamics. The solid line indicates a fit of the standard Williams-Landel-Ferry (WLF) temperature dependence to the data for the lower molecular weight sample. Values of M are in g mol1.

Fig. 2.56 Beating of Kiessig fringes observed using X-ray reflectivity from a PVP PS-PVP tri block copolymer film (fes = 0.48, Mv = 120 kg mol ) with two discrete thicknesses of 1935 and 2229 A (de Jeu et al. 1993). The difference in height results from island and hole formation at the free surface, and is equal to the bulk domain spacing.

Fig. 56 Shear alignment of a PS-PVP(PDP)x polymer and TEM micrograph of the resulting mixture. Reprinted with permission from [205]...

The very small widths of such interfaces lead to little penetration of A chains into B chains, and vice versa, and thus very few entanglements are made across the interface. This lack of entanglement across the interface is thought to be responsible for the very low adhesion, as represented by the fracture energy Qc of such interfaces. For example, the Qc of the PS/PVP interface is about 1.5 J/m2 whereas the Qc of the PS homopolymer is -500-1000 J/m2. Significantly, a polymer pair with a smaller positive value of y, PS/poly(methylmethacrylate) (PM-MA) which has a y 0.03 and thus a value of a,-3.2 nm,has a considerably larger Qc 10 J/m2. 

Fig-i- Theoretical volume fraction vs. distance profile across an interface between PS and PVP polymers. A value of x = 0-12 appropriate to a temperature of 160 °C [ 105] has been used to predict an interface width a7 of 1.6 nm from Eq. (3). This profile is consistent with neutron reflectivity measurements of PS/PVP interface segment density profiles if the apparent broadening of the interface by capillary waves is taken into account [ 106]... 

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