  We carried out a cyanopolyyne line survey towards a large sample of HMSFRs
using the Shanghai Tian Ma 65m Radio Telescope (TMRT). Our sample consisted of
123 targets taken from the TMRT C band line survey. It included three kinds of
sources, namely those with detection of the 6.7 GHz CH3OH maser alone, with
detection of the radio recombination line (RRL) alone, and with detection of
both (hereafter referred to as Maser-only, RRL-only, and Maser-RRL sources,
respectively). We detected HC3N in 38 sources, HC5N in 11 sources, and HC7N in
G24.790+0.084, with the highest detection rate being found for Maser-RRL
sources and a very low detection rate found for RRL-only sources. Their column
densities were derived using the rotational temperature measured from the NH3
lines. And we constructed and fitted the far-infrared (FIR) spectral energy
distributions. Based on these, we derive their dust temperatures, H2 column
densities, and abundances of cyanopolyynes relative to H2. The detection rate,
the column density, and the relative abundance of HC3N increase from Maser-only
to Maser-RRL sources and decrease from Maser-RRL to RRL-only sources. This
trend is consistent with the proposed evolutionary trend of HC3N under the
assumption that our Maser-only, Maser-RRL, and RRL-only sources correspond to
massive young stellar objects, ultra-compact HII regions, and normal classical
HII regions, respectively. Furthermore, a statistical analysis of the
integrated line intensity and column density of HC3N and shock-tracing
molecules (SiO, H2CO) enabled us to find positive correlations between them.
This suggests that HC3N may be another tracer of shocks, and should therefore
be the subject of further observations and corresponding chemical simulations.
Our results indirectly support the idea that the neutral--neutral reaction
between C2H2 and CN is the dominant formation pathway of HC3N.
