Abstract

Using collaborative patent data from 882 new R&D institutions in the Yangtze River Delta from 2011 to 2024, this paper examines how city‑level industry‑university‑research collaboration networks have changed over time and what drives their formation. We map patent co‑applications to city pairs, analyze the network using social network indicators, core‑periphery analysis, and cohesive subgroup analysis, and then test the effects of multidimensional proximity using QAP correlation and regression models. Four findings stand out. First, the inter‑city network expanded rapidly, while its density followed a V‑shaped path. The structure became flatter, more accessible, and with increasingly small‑world features. Second, the network shifted from an early point‑to‑point pattern to corridor‑based growth, then to a denser, networked structure. Cities such as Hangzhou, Nanjing, Shanghai, and Hefei became important hubs, but differed sharply in their network functions. Third, the network retained a clear core‑periphery pattern. A small number of cities formed a highly connected core, while many newly connected cities remained peripheral. Fourth, geographical, economic, and organizational proximity promoted collaboration, whereas institutional and technological proximity were negatively associated with tie formation. The findings suggest that new R&D institutions are not only local innovation actors but also relational platforms that reshape regional innovation networks. Policy should therefore combine support for core hubs with stronger mechanisms for cross‑boundary resource sharing and integration with peripheral cities.