# chemfig/chemmacros: Line thickness of polymer brackets

It seems that polymer brackets designed by chemmacros produce slightly thicker lines than the rest of the formula from chemfig. Is there a way to get polymer brackets with same line width as in the formula?

\documentclass{scrreprt}
\usepackage{chemfig} %Structural formulas
\usepackage{chemmacros} %Polymer brackets
\chemsetup{modules={polymers}}

\begin{document}
\begin{figure}
\centering
\chemfig{[-1]H-[@{a}]O-[1]-[-1]-[@{b}1]O-[-1]*6(-=-(-[-1](<[:240])(<:[:300])-[1]-[-1](<[:240])(<:[:300])-[1])=-=)}
\makepolymerdelims[subscript={x}]{12pt}{a}{b}
\end{figure}
\end{document}


The brackets are not drawn with TikZ. chemmacros just provides an interface for an idea presented in the chemfig manual. There the brackets are math delimiters, basically something like
$\left.\vrule height<dim> depth<dim> width0pt\right]$

What you can do is changing the bonds' thickness with \setbondstyle{line width=...} (see the chemfig manual for details) instead.