*Article* **Experimental Study on High-Performers Quaternary Copolymer Based on Host–Guest Effect**

**Tao Xu , Jincheng Mao \* , Yang Zhang \*, Xiaojiang Yang, Chong Lin, Anqi Du, Heng Zhang, Quan Zhang and Jinhua Mao \***

> State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China; 15827742134@163.com (T.X.); xjyang@swpu.edu.cn (X.Y.); 201999010016@swpu.edu.cn (C.L.); 13880147377@163.com (A.D.); 201811000155@stu.swpu.edu.cn (H.Z.);

zhangsanfengdbsy@163.com (Q.Z.)

**\*** Correspondence: jcmao@swpu.edu.cn (J.M.); 201521000202@stu.swpu.edu.cn or yangzhang10234@163.com (Y.Z.); 201921000706@stu.swpu.edu.cn or 18328085244@163.com (J.M.); Tel.: +86-28-8303-3546 (J.M. & Y.Z. & J.M.)

**Abstract:** A quaternary polymer (HGP) was prepared by the free-radical polymerization of acrylamide, acrylic acid, maleic anhydride functionalized *β*-cyclodextrin (MAH-*β*-CD), and N-(3 methacrylamidopropyl)-N, N-dimethylnaphthalen-1-aminium chloride (NAP). It was found that host–guest behavior occurred most effectively at a molar rate of NAP and CD with 1:1, which exhibited better solubility than hydrophobically associative polymer. Moreover, the as-prepared polymer has superior salt tolerance, shear resistance, and viscoelasticity due to host–guest strategy. More importantly, the HGP solution simulates the distribution of formation water in the Bohai SZ1-1 oilfield has good rheological properties at 120 ◦C. All results show that the proposed polymer could be a competitive candidate in oilfield applications such as fracturing fluids, displacement fluids, and drilling fluids.

**Keywords:** host–guest strategy; hydrophobically associating water-soluble polymers; rheological behaviors; salt tolerance; *β*-cyclodextrin
