## 3 Results and Discussion  
### Synthesis of Bottlebrush Polymer  
First, we synthesized a linear-_block_-brush bottlebrush polymer, PCNB-_b_-P (NB-PSt), via sequential ring-opening metathesis polymerization (ROMP) initiated with Grubbs catalyst G3. The synthesis employed the monomer _tert_-butyl 5-norborne-2-carboxylate (a mixture of endo-/exo-isomers with a molar ratio of 8:2, _t_BNB) and the macromonomer norbornene-terminated polystyrene (NB-PSt) [44; 45], followed by hydrolysis with trifluoroacetic acid (TFA) in dichloromethane (DCM) (Figures 1 and S1). This hydrolysis step cleaves the _tert_-butyl groups from the linear PfBNB block, liberating carboxyl groups and forming the PCNB block, which serves as a distinctive sidechain for the final bottlebrush polymer PCNB\({}_{a}\)-_b_-P (NB-PSt\({}_{n}\))\({}_{b}\). Here, \(a\) and \(b\) denote the degree of polymerization (DP) of the PCNB and P (NB-PSt) brush blocks, respectively, while \(n\) represents the DP of the macromonomer NB-PSt. The macromonomer NB-PSt was synthesized via atom transfer radical polymerization (ATRP) using norbornene-functional bromide (NB-Br) as the ATRP initiator; details of the synthesis and characterization are provided in Figures S1-S3. The structural parameters of NB-PSt, including a polymerization degree (_n_) ranging from 25 to 80 and a molecular weight polydispersity (_D_) of less than 1.25 (Table S1), attest to the good quality of the prepared macromonomers. The relative length ratio of the linear PCNB block to the neighboring densely grafted PSt sidechains, \(a/n\), is a crucial parameter in our strategy as a heterogeneous sidechain. Generally, the sidechains at the two ends of the wormlike bottlebrush polymer have a relatively larger void space compared to those at the side positions [46]. This \"end effect\"-induced regioselectivity significantly enhances the performance of a single PCNB chain located at the end of the bottlebrush polymer when it acts as a nucleating agent for silica deposition. Furthermore, as a special single sidechain, if \(a\) is much smaller than \(n\), the screening effect of the relatively longer neighboring densely grafted PSt sidechains on the buried single PCNB chain will significantly retard further silica deposition. Conversely, if \(a\) is far larger than \(n\), the long and flexible PCNB chain may coil around the brush part due to conformational changes, causing the diffusion of nucleating sites for silica deposition. Therefore, we set \(a/n>1\) and close degrees of polymerization (DP) for both the PCNB and PSt sidechains. Notably, \(a/n>1\) should be the boundary condition for using such a single PCNB heterogeneous sidechain as a nucleating agent for silica deposition. The structural parameters of the linear-_block_-brush polymers were confirmed by a combination of \({}^{1}\)H NMR and gel permeation chromatography (GPC) techniques. The first P\(t\)BNB block was synthesized via ring-opening metathesis polymerization (ROMP) with nearly 100% monomer conversion of \(t\)BNB, as evidenced by the complete disappearance of peaks 1 and 2 in Figure 2a and the appearance of signals 1\({}^{\prime}\) and 2\({}^{\prime}\) in Figure 2b. Notably, to reduce costs, we employed an endo- and exo-mixture of \(t\)BNB, which resulted in the splitting of signals from protons 1 and 2, as highlighted by the red box in Figure 2a. After the second ROMP with NB-PSt, the signal ranging from 5.1 to 5.8 ppm diverged into two peaks, which could be attributed to the overlap of protons 4\({}^{\prime}\) and 5\({}^{\prime}\) on the backbone of the P (NB-PSt) block and protons 1\({}^{\prime\prime}\) and 2\({}^{\prime\prime}\) (Figure 2d). Following hydrolysis with TFA, the insoluble PCNB chain generated in CDCl\({}_{3}\) led to a significant decrease in the signals from protons 1\({}^{\prime\prime\prime}\) and 2\({}^{\prime\prime\prime}\) (Figure 2e), as well as the disappearance of the sharp peak 3\({}^{\prime\prime}\)+7\({}^{\prime}\) (Figure 2d).