Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Reacting Polymers with Highly Correlated Initial Conditions   We propose and theoretically study an experiment designed to measure short
time polymer reaction kinetics in melts or dilute solutions. The photolysis of
groups centrally located along chain backbones, one group per chain, creates
pairs of spatially highly correlated macroradicals. We calculate time-dependent
rate coefficients $\kappa(t)$ governing their first order recombination
kinetics, which are novel on account of the far-from-equilibrium initial
conditions. In dilute solutions (good solvents) reaction kinetics are
intrinsically weak, despite the highly reactive radical groups involved. This
leads to a generalised mean field kinetics in which the rate of radical density
decay $-\ndot \twid S(t)$ where $S(t)\twid t^{-(1+g/3)}$ is the {\em
equilibrium} return probability for 2 reactive groups, given initial contact.
Here $g\approx 0.27$ is the correlation hole exponent for self-avoiding chain
ends. For times beyond the longest coil relaxation time $\tau$, $-\ndot \twid
S(t)$ remains true, but center of gravity coil diffusion takes over with rms
displacement of reactive groups $x(t)\twid t^{1/2}$ and $S(t)\twid 1/x^3(t)$.
At the shortest times ($t\lsim 10^{-6}$ sec), recombination is inhibited due to
spin selection rules and we find $\ndot \twid t S(t)$. In melts, kinetics are
intrinsically diffusion-controlled, leading to entirely different rate laws.
During the regime limited by spin selection rules, the density of radicals
decays linearly, $n(0)-n(t)\twid t$. At longer times the standard result
$-\ndot\twid dx^3(t)/dt$ (for randomly distributed ends) is replaced by
$\ndot\twid d^2x^3(t)/dt^2$ for these correlated initial conditions. The long
time behavior, $t>\tau$, has the same scaling form in time as for dilute
solutions.

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The categories of this paper are: math
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
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The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: astro-ph