Minor chain

Fig. 4. (a) Motion of minor chains that have poked through from one side of the interface, (b) Growth of the minor chain spherical envelopes that have emerged from side of the interface. 

The molecular properties H t), determined by the minor chain model (Table 1), are interrelated and have a convenient common scaling law. The dynamic proper-... 

Significant experimental support for these relations and the minor chain repta-tion model has been obtained from neutron reflection and SIMS experiments using specially deuterated polymers... 

We present here a simple experiment, conceived to test both the reptation model and the minor chain model, by Welp et al. [50] and Agrawal et al. [51-53]. Consider the HDH/DHD interface formed with two layers of polystyrene with chain architectures shown in Fig. 5. In one of the layers, the central 50% of the chain is deuterated. This constitutes a triblock copolymer of labeled and normal polystyrene, which is, denoted HDH. In the second layer, the labeling has been reversed so that the two end fractions of the chain are deuterated, denoted by DHD. At temperatures above the glass transition temperature of the polystyrene ( 100°C), the polymer chains begin to interdiffuse across the... 

When M M, disentanglement is nearly instantaneous but approaches tro when M 8Me, which is the strain hardened (A. 4) upper bound for chain pullout without bond mpture. For welding, the relaxation times Trq refer to the minor chains of length /(/) such that the retraction time is approximated by Tro /(/). When M > 8Me, the chains cannot disentangle completely at the Rouse time and... 

The stored strain energy in the interface of volume proportional to X is consumed in disentangling the minor chains and we obtain... 

For such free surfaces with no energetic preference of the surface for one of the components (because of the arbitrary choice of a purely symmetric choice of interactions, UAA=UBB ) the surface enrichment effects are typically rather weak (Fig. 16b), even if one considers asymmetry of chain lengths. Even for %=0 the shorter chains are then attracted to the surface, but this purely entropic effect is particularly weak. For the enthalpy is less effective near the free surface in comparison with the entropy of mixing, and this effect is for small volume fraction < >A b of the minority component nearly independent of the asymmetry in chain length (Fig. 16b) i.e., even if the minority chains are much longer (NA= 2Nb) they segregate to the surface, contrary to the non-interacting case. 

Nitric oxide traps all chain carriers by reaction (5) and suppresses chain sensitization, reaction (4 ). The consistently low Arrhenius parameters reported in the early diethylperoxide studies are thus a result of a minor chain decomposition propagated by reaction (4 ). The main reaction mechanisms postulated for... 

X > Xcrii. one finds even a gradual collapse of the minority chains [102]. 

In the reptation dynamics model, proposed by de Gennes and Edwards, " individual polymer chains are conjectured to move like Brownian snakes in a field (tube) of topological constraints imposed by entanglements from neighbouring chains, (Fig. 1) at f = 0. At time h, some end portions of the chain (these are called the minor chains ) have already escaped from the initial tube by reptation. 

The structure of the diffuse weld interface resembles a box of width X, with fractal edges containing a gradient of interdiffused chains as shown by Wool and Long. When the local stress at a crack tip exceeds the yield stress, the deformation zone forms and the oriented craze fibrils consist of mixtures of fully entangled matrix chains and partially interpenetrated minor chains. 

Fracture of the weld occurs by disentanglement of the minor chains, or bond rupture. In the VP theory, many properties follow scaling laws dependent on the difference between p, the occupational probability of the lattice and the percolation threshold Pc, the minimum concentration (occupational probability) at which connectivity could occur in an infinite lattice. In particular, the fracture toughness, which depends on this percolation term, Gic [p - Pc], determines the number of bonds to be broken, or disentangled. 

Figure 11.28 The interdiffusion process at a polymer-polymer interface (57) (a) appearance of the minor chains and (b) the minor chain spherical envelopes.

One of the major problems in modern polymer science relates to the understanding and verification of the relations governing diffusion in the very short time interval, when polymer chains just leave the de Gennes tube see Section 5.4.2. Wool and co-workers (3,42) developed the minor chain model, indicating that the diffusion of polymer chains in the melt should scale as see Sections S.4.2.2 and 11.5. 

How does the minor chain reptation model work with reference to the ripple experiment (Please limit description to 100 words and a drawing.)... 

The average monomer interpenetration depth of segments on the interdiffusing chains, jc(0, is obtained from an integration over the Gaussian segment density profiles of the inter-diffused minor chain population,(2i) such that... 

The number of monomers that have crossed from one side of the interface to the other is equivalent to the total interpenetration contour length, LqCO = n(t)l(t). By summing over the segment density profiles of the interdiffused minor chains, one obtains... 

The NMR studies of copolymers containing an amide comonomer revealed some peculiarities. In all amide copolymers the amount of saturated end groups was higher than the amount of double bonds. Termination by chain transfer to aluminum results in the polymer chains having Al-C bonds, which normally undergo hydrolysis to saturated end groups during the polymer workup [140]. It has been reported that transfer to aluminum, which is normally a minor chain termination mechanism in metallocene-mediated polymerizations, may become... 

Glu Rich Mature Toxin Region (Minor Chain)... 

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