Mildly Rewritable Polymer Brushes Enabled by Multiple Hydrogen Bonds of Complementary Nucleobases

ABSTRACT

Functional surfaces from rewritable polymer brushes find numerous applications. However, the rewritable properties mainly rely on surface structural variations or chemical compositions changes through stimuli‐response, often confronting with low binding, poor reversibility, and harsh treatment conditions. Herein, we develop a robust supramolecular approach to fabricating mildly rewritable polymer brushes by harnessing multiple hydrogen bonds (MHBs) between bioinspired complementary nucleobases. A “grafting from” strategy is employed to prepare dense nucleobase‐containing polymer brushes, which anchor complementary nucleobase‐functionalized copolymers with distinct hydrophilic blocks for properties tunability. MHBs between complementary nucleobase‐containing polymers are strong enough to tailor the surface properties regardless of chain lengths and chemical compositions of the hydrophilic blocks. As such, various rewritable polymer brushes with thermoresponsive, pH‐responsive, and varied protein‐resistant properties are generated and changed in between. More significantly, the dynamic reversibility of MHBs imparts excellent cyclic stability of properties variation to the rewritable polymer brushes. Finally, the controlled capturing and releasing of proteins in aqueous solutions are achieved, showcasing potential applications of the rewritable polymer brushes for the bioconcentration of proteins. Collectively, this work offers us with a novel and efficient strategy for tailoring surface properties of polymer brushes, which might amplify their applications in biomedical fields.

A supramolecular approach based on multiple hydrogen bonds of complementary nucleobases is developed for constructing rewritable polymer brushes, endowing tunable surface properties and efficient reversible modifications. This work offers us with a novel and efficient strategy for tailoring surface properties of polymer brushes, which might amplify their applications in biomedical fields.

1. Introduction

Surface modifications with covalently attached polymers have gradually emerged in the last two decades [1, 2, 3, 4], owing to the numerous applications of attained polymer materials such as biosensing [5, 6], bioseparation [7], photonic crystals [8], and dielectric materials [9]. Both “grafting‐from” and “grafting‐to” methods have been utilized for anchoring polymers to surfaces [10]. Surface‐attached polymers through the “grafting‐to” approach is usually limited to the relatively low grafting densities due to the high steric hindrance for reacting with the end‐group of a preformed polymer chain [11, 12, 13]. Conversely, the “grafting‐from” method from surface‐attached initiators is capable of achieving higher grafting densities and thicker polymer layers [14, 15, 16, 17]. Additionally, compared with the random coil conformation of sparsely grafted polymers, densely grafted polymer chains from the “grafting‐from” method typically adopt a stretched conformation in the brush regime, which is preferred for further surface polymer modifications [18].

Polymer brushes with rewritable surfaces are highly pursued by scientists since they can be applied for reversible patterning [19], anti‐counterfeiting [20], and information encryption [21]. Simultaneously, they are also of great significance for materials reusability and sustainability [22]. Two major strategies are successfully developed to achieve the rewritability of functional surfaces. The first one is based on the responsive alteration of polymer structures, contributing to the rewritable surface properties [23, 24]. These processes are usually triggered by structural changes via UV lights [25], electric field [26], magnetic field [27], and so on, while substantially maintaining the chemical compositions of the surface. Notably, most of the fabricated rewritable surfaces by this approach only present the ON/OFF switching activity [25, 28]. In contrast, the other strategy depends on the reversible chemical composition change of the polymer surfaces through dynamic covalent bonds [29], electrostatic interactions [30], host‐guest interactions [31, 32], hydrogen bonds [33, 34], to name a few. The remarkable change of the surface chemical composition brings about significant tunability of the surface properties [35]. Meanwhile, the properties of the rewritable surfaces can be gradually altered by controlling the chemical composition variation, which is highly desired for multifunctional polymer materials [36].

Distinct methods have been harnessed to fabricate rewritable polymer brushes via reversible chemical composition changes, but there are still some issues which drastically hinder their widespread applicability, including high temperature requirement, low binding strength, and poor reversibility (Scheme 1). Due to the relatively weak interactions of dynamically reversible non‐covalent bonding, the efficient formation of rewritable polymer brushes is often confined to happen under special conditions. For example, multiple hydrogen bonds (MHBs) of singe nucleobase in polymer chain ends are capable of forming polymer brushes in low polar organic media, which is destroyed under high polar solvents (Scheme 1a) [33, 34, 37, 38]. Alternatively, dynamic covalent bonds provide a robust and stable bonding to achieving rewritable polymer brushes (Scheme 1b) [29]. However, the high steric hindrance for the access of small reactive groups also leads to poor reversibility and harsh reaction condition requirements such as high temperatures for renewing the surface. Consequently, it is still highly challenging to construct functional polymer brushes, which possess mildly rewritable surfaces for efficient functionalization and properties tunability.

SCHEME 1.

Schematic illustration of rewritable polymer brushes through (a) multiple hydrogen bonds of single nucleobase, (b) dynamic covalent chemistry linkage, and (c) multiple hydrogen bonds of nucleobase‐containing polymers in this work.

Herein, we have successfully utilized MHBs between complementary nucleobases to endow polymer brushes with mildly rewritable properties. Both adenine and thymine‐containing polymer brushes were synthesized through the “grafting‐from” approach via surface reversible addition‐fragmentation chain transfer (surface RAFT) polymerization. Distinct amphiphilic diblock copolymers with complementary nucleobases were introduced to the polymer brushes for functionalization. Regardless of the chain lengths and chemical compositions of hydrophilic blocks, the strong MHBs between complementary nucleobases‐functionalized polymers are robust enough to achieve efficient surface modifications (Scheme 1c). The dynamic reversibility of MHBs bestows the functional surface with extraordinary rewritable properties, showing several cycles without obvious performance decay. As such, it is feasible to fabricate rewritable thermoresponsive and pH‐responsive polymer brushes. Further, the reversible writing‐erasing process enables us to effectively tune the surface properties from protein resistance to protein adsorption. To showcase the applicability of this unique properties, we demonstrate the controlled capturing and releasing of proteins in aqueous solutions by employing the rewritable polymer brushes. This work provides us with an outstanding supramolecular approach for tailoring surface properties of polymer brushes, which is promising to find applications in various fields such as biosensing, bioseparation, and photonic crystals.

2. Results and Discussion

2.1. Fabrication of Nucleobase‐Functionalized Polymer Brushes

Nucleobase‐functionalized brushes were constructed through surface RAFT polymerization with 3‐(adenine‐9‐yl)propyl acrylamide (AAm) and 3‐(thymin‐1‐yl)propyl acrylamide (TAm) (Figure 1a, Schemes S1 and S2, and Figures S1 and S2) [39]. Here, surface RAFT polymerization was carried out by anchoring a chain transfer agent (CTA), which contains a disulfide pentagonal ring, on gold substrates (Figure 1a, Schemes S3 and S4, and Figures S3 and S4). The water contact angles (WCAs) of PAAm₂₀ and PTAm₂₀ brush (abbreviated as PA and PT brush) are 54.5° and 62.0° decreasing from the WCA of 101.1° for the CTA‐attached gold (Au‐CTA), indicating the successful construction of polymer brushes (Figure 1b). The hydrophilicity of PA/PT brush can be attributed to the hydrogen bonding between the immobilized amide/nucleobase groups and water. The attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectra shown in Figure 1c exhibit characteristic absorption peaks at 3335, 2990, 1660, and 1110 cm⁻¹, corresponding to the ─NH─ stretching vibration from the amide group, the C─H stretching vibration from main chain, the purine ring, and the C═S stretching vibration, respectively. Furthermore, compared to the X‐ray photoelectron spectroscopy (XPS) results of Au‐CTA (Figure S5), the appearance of strong N 1s signal in the XPS spectra of PA and PT brush confirms the successful grafting of PA and PT (Figure 1d–f).

FIGURE 1.

(a) Schematic illustration of synthesizing PA/PT brush mediated by surface RAFT polymerization. (b) WCAs, (c) ATR‐FTIR, and (d) XPS spectra of Au‐CTA, PA, and PT brush. N 1s and S 2p high‐resolution spectra of (e) PA and (f) PT brush.

During the surface RAFT process, free CTA was co‐added for better controlling the polymerization process, as well as minimizing the difference between the polymer in brushes and that in solution. On this basis, the obtained PA and PT in the solution were characterized via size exclusion chromatography (SEC) to represent the polymers in brushes (Figure S6) [40]. The low dispersity ($\mathrm{Ð}$) for both polymers of 1.12 illustrates good control over the polymerization. Therefore, a uniform distribution of polymer chain lengths was obtained in PA/PT brushes. Furthermore, ellipsometry was used to measure dry thickness evolution before and after grafting polymer layers (Table S1). The CTA layer presented a thickness of 4.0 nm, and after grafting the PA brush the thickness increased to 6.8 nm. Based on the number‐average molar mass (M _n) of PAAm₂₀, a grafting density of 0.76 chains nm⁻² was yielded, demonstrating the formation of relatively dense nucleobase‐containing polymer brushes from surface RAFT.

2.2. Rewritable Polymer Brushes Mediated by MHBs of Nucleobases

MHBs of complementary nucleobases are capable of forming strong bonding for modulating the morphologies of polymer nanostructures in aqueous solutions [41, 42]. We wonder if the robust MHBs of nucleobases are able to overcome the strong steric hindrance of dense polymer brushes for rewritable surfaces. Different adenine and thymine‐containing diblock copolymers with poly(N,N‐dimethylacrylamide) (PDMA) as the hydrophilic block were prepared and characterized through ¹H NMR spectroscopy and SEC (Scheme S5 and Figures S7–S10). Initially, the binding of PDMA₈₀‐b‐PTAm₂₀ (PDMA‐PT) to the PA brush was in situ monitored by using quartz crystal microbalance with dissipation (QCM‐D). An obvious negative frequency (Δf) shift and a positive dissipation (ΔD) shift were observed (Figure 2a), suggesting the formation of the PDMA‐PT@PA brush. Besides, the dry thickness of the polymer layer increases to 12.7 nm, suggesting a grafting density of 0.35 chains nm⁻² of the PDMA‐PT brushes (Table S1). This high graft density certifies the effectiveness of our method through MHBs between the complementary nucleobases‐functionalized polymers. In stark contrast, the introduction of a diblock copolymer solution containing the same nucleobase (PDMA₈₀‐b‐PAAm₂₀) to the PA brush only resulted in much smaller Δf and ΔD shifts (Figure 2b). These results indicate that the complementary hydrogen bonding interaction is much stronger than the interaction between non‐complementary nucleobases only through π–π stacking or hydrophobic interactions.

FIGURE 2.

Frequency (Δf) and dissipation (ΔD) shifts during hydrogen bonding recognition procedure on PA brush with (a) PDMA‐PT and (b) PDMA₈₀‐b‐PAAm₂₀ as well as during the subsequent DMF rinsing. (c) Atomic percentage evolution of N and S elements with/without PDMA‐PT on PA brush. (d) WCA changes during five re‐writing cycles on the PA brush with PDMA‐PT adsorption and desorption. Δf and ΔD shifts during PDMA‐PT adsorption on the PA brush and subsequent rinsing process with (e) urea solutions and (f) buffer solutions of different pH values.

Interestingly, it is observed that the PDMA‐PT@PA brush undergo reversible renewability upon rinsing with dimethyl formamide (DMF) (Figure 2a). DMF has carbonyl and dimethylamine groups, both of which provide lone pair electrons for hydrogen bonding. Therefore, it can interact with both adenine and thymine for forming intermolecular hydrogen bonds. This process significantly increases the conformational entropy of the polymers, disrupting the MHBs of complementary nucleobases [43]. The in situ QCM‐D measurements manifest the highly reversible and rewritable properties of the nucleobase‐containing polymer brushes over two consecutive writing‐erasing cycles. Meanwhile, ATR‐FTIR spectra show that the peak intensity of the pyrimidine ring at 1660 cm⁻¹ increases after introducing PDMA‐PT, while the C─H stretching vibration peak at ∼2900 cm⁻¹ weakens due to the masking influence of the upper PDMA block (Figure S11). After the desorption with DMF, the characteristic peaks of the PA brush all recovered (i.e., the regenerated PA brush). Further, XPS and corresponding atomic percentages are also compared for the rewritable polymer brushes (Figure 2c, Figures S12–S14, and Table S2). After the binding of PDMA‐PT, the atom ratio of N element obviously increases because of more N atoms in the PDMA block with the simultaneous decline of S element from the CTA segment. After rinsing with DMF, the atomic percentages of N and S elements almost return to the original state (Figure 2c).

In addition, the thickness of the polymer layer also confirms the reversible rewritability of the polymer brushes, changing from the initial 6.8 nm of the PA brush, to 12.7 nm of the PDMA‐PT@PA brush, then to 6.0 nm of the regenerated PA brush (Table S1). More importantly, WCA measurements show that the rewritable properties of the nucleobase‐containing polymer brushes can be repeated for many cycles without obvious decay. Due to the exposed hydrophilic PDMA block and the carboxyl end group, the formation of the PDMA‐PT@PA brush results in an obvious decrease of WCA to 35.8° (Figure 2d). Upon desorption of PDMA‐PT, the WCA restored to 52.8°, which is consistent to the WCA of the initial PA brush. WCA results indicate the reversible and repeated rewritability of the surface properties can be achieved by using the MHBs of complementary nucleobases. This behavior was also realized with other PDMA_m‐b‐PTAm₂₀ copolymer with varied block lengths of hydrophilic PDMA (Figures S15 and S16). The brushes construction of PT@PA and the stability of MHBs in water were confirmed by a control QCM‐D experiment of extended duration test (Figure S15d). Likewise, when first preparing PT brush, adenine‐containing block copolymers (PDMA_m‐b‐PAAm₂₀) can also be used to implement reversible rewritability of the polymer brushes (Figures S17 and S18). These results suggest the use of MHBs of nucleobase‐containing polymers in aqueous solutions is a general and robust method to fabricate rewritable surfaces.

In order to expand the rewritable polymer brushes for biological systems, various aqueous solutions were explored for the desorption by disrupting the MHBs. Urea is widely used as a classical hydrogen bonding destroying agent. As shown in Figure 2e and Figure S19, a certain concentration of urea (e.g., 3–4 m) is proven effective for detaching the added diblock copolymer PDMA‐PT from the substrate. In addition, due to the relatively low pK _a of the ─NH─ group in thymine ring of PTAm [44], a mild pH change was explored to regulate the formation and dissociation between PTAm and PAAm segments. As characterized by QCM‐D (Figure 2f), the aqueous solution of pH 10.0 results in the restoration of Δf/ΔD to baseline, suggesting successful dissociation of the grafted diblock copolymer under this condition. Accordingly, ranging from DMF treatment to urea solution and then to pH regulation, the reversible complementary hydrogen bonds between PAAm and PTAm can be regarded as a general platform for surface rewriting, and provide a highly versatile route to construct functional/responsive interface and to facilitate the subsequent erasing and rewriting.

2.3. Rewritable Responsive Polymer Brushes Fabricated Through MHBs

Responsive polymer brushes play a significant role in realizing multifunction [45], while robust yet renewable surfaces are barely fabricated. The modular strategy through complementary nucleobase interactions provides a straightforward method for constructing rewritable responsive surfaces. In order to rule out the influence of breaking supramolecular interactions, the stability of complementary hydrogen bonds between the PA brush and PTs for withstanding elevated temperatures was first studied by monitoring the thermal change of the PDMA‐PT@PA brush with QCM‐D (Figure S20). After heating at 50°C for 40 min and then cooling to 25°C, both Δf and ΔD almost restored to their original values, indicating that PDMA‐PT binds to the PA brush steadily within the heating‐cooling process. This result certifies the robust feature of the grafting strategy under modest temperatures. The Δf and ΔD shifts on the PA brush at 50°C were then collected as the references to eliminate temperature effects on Δf and ΔD (Figure S21a). It is noticed that the temperature change induces the similar Δf shift on PA brush to that on PDMA‐PT@PA brush (Figure S21b), indicating the non‐responsive feature of PDMA block and the thermally stable binding between the PA brush and PT containing diblock copolymers.

For preparing thermal responsive surfaces, thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) was selected by binding the diblock copolymer of PNIPAM₃₀₀‐b‐PTAm₂₀ (PNIPAM‐PT) to the PA brush. PNIPAM‐PT can be easily synthesized through sequential RAFT polymerizations, and the aqueous solutions of PNIPAM‐PT present the cloud point of 30°C from the UV–vis measurements (Scheme S6 and Figures S22–S24). After grafting PNIPAM‐PT, much larger Δf and ΔD shifts for the PNIPAM‐PT@PA brush are generated at 50°C compared to the references (Figure 3a and Figures S20 and S21). In addition, during the heating‐cooling processes, distinct variations in the slopes of Δf and ΔD curves are observed at ∼32°C, implying a phase transition. By subtracting the Δf/ΔD shifts from the reference PA brush, relative Δf/ΔD shifts (Δf _r/ΔD _r) originated from the thermal response of PNIPAM are obtained (Figure 3b,c). Obviously, Δf _r starts to increase at ∼32°C and then levels off at ∼36°C, indicating that PNIPAM chains change from a hydration state to a dehydration state (Figure 3b). Meanwhile, ΔD _r displays a reduction during heating, validating the transformation from extended to collapsed conformations along with dehydration (Figure 3c). A reversed change during the subsequent cooling process on Δf _r/ΔD _r demonstrates the re‐hydration and re‐swelling of PNIPAM in the PNIPAM‐PT@PA brush. Along with the phase transition of PNIPAM, the surface wettability varied with WCAs changing from 35.6° to 55.4° and then decreasing to 36.0° during one heating–cooling cycle (Figure 3d). These hydrophilic‐hydrophobic transitions were carried out for at least four cycles without obvious performance degradation (Figure 3d).

FIGURE 3.

(a) Frequency (Δf) and dissipation (ΔD) shifts during the hydrogen bonding recognition procedure of PNIPAM‐PT on the PA brush and the subsequent temperature response. Comparison on (b) Δf changes and (c) ΔD changes between the PNIPAM‐PT@PA brush and the PA brush during heating‐cooling process. Δf _r and ΔD _r represent the differences between the two brushes. (d) WCA evolution on the PNIPAM‐PT@PA brush during four thermal responsive cycles. (e) Frequency (Δf) and dissipation (ΔD) shifts during the hydrogen bonding recognition procedure of PAG‐PT on the PA brush and the subsequent pH response. (f) WCA evolution on the PAG‐PT@PA brush during five pH responsive cycles.

pH responsive surfaces are also highly desired for various applications [46, 47]. Acryloyl glycine (AG) carrying a carboxyl group was used to obtain a pH responsive diblock copolymer PAG₈₀‐b‐PTAm₂₀ (PAG‐PT) (Scheme S7 and Figures S25–S28). As shown in QCM‐D data (Figure 3e), the introduction of PAG‐PT aqueous solution resulted in obvious Δf and ΔD shifts, verifying the successful grafting of PAG to form the PAG‐PT@PA brush. Subsequently, when circularly switching the solution pH between 4.0 and 7.0, remarkable Δf and ΔD shifts were observed. The carboxyl groups are protonated at pH 4.0, so the PAG layer adopts a more collapsed conformation and shows partial dehydration, leading to an increase in Δf and a decline in ΔD. Conversely, the negatively charged carboxyl groups at pH 7.0 make the PAG layer swollen and extended. This pH switch was performed for at least four cycles with outstanding repeatability. WCA measurements were further employed to characterize the wettability changes at different pH conditions, showing a WCA change from 51.6° at pH 4.0 to 21.3° at pH 7.0 (Figure 3f). Such hydrophilic‐hydrophobic switching was circularly performed for five cycles without distinct performance decay (Figure 3f), demonstrating the remarkable stability and feasibility as a rewritable pH responsive surface. These results highlight that multiple hydrogen bonding interactions of nucleobases can act as a robust bonding, enabling facile and efficient surface modifications for functionalization.

2.4. Modulating the Interactions of Rewritable Polymer Brushes with Proteins

Non‐specific protein adsorption on biomaterials is an extreme threat for their functional applications, which potentially leads to response failure, immune, and inflammatory reactions [48]. The fabrication of biocompatible surfaces with anti‐biofouling properties is highly appealing, and polyethylene glycol (PEG) has been widely utilized as an outstanding protein resistant material [49]. Here, thymine‐functionalized copolymer containing a PEG block (PEG₄₅‐b‐PTAm₂₀, PEG‐PT) was prepared through RAFT polymerization (Scheme S8 and Figures S29–S31). The in situ grafting of PEG‐PT on PA brush to yield the PEG‐PT@PA brush and the subsequent protein resistance tests were monitored with QCM‐D (Figure 4a,b). Following the introduction of PEG‐PT solution, the negative Δf shift after PBS rinsing verifies the effective grafting of the PEG‐containing brush. Subsequently, lysozyme (Lyz) and bovine serum albumin (BSA) were used as model proteins to study protein resistance property. Clearly, no visible Lyz/BSA adsorption were observed to stay on the surface after PBS buffer rinsing, demonstrating remarkable protein resistance of the PEG‐PT@PA brush. Further, the PA brush can be recovered to the initial state by rinsing with DMF (Figure 4a,b). On the contrary, either the PA (Figure S32) or PAG‐PT@PA brush (Figure S33a,b) gives rise to obvious protein adsorption. The PDMA‐PT@PA brush also displays some ability in protein resistance (Figure S33c,d), probably due to the relatively high hydration and hydrophilicity of PDMA. Further raising the protein concentration to 5.0 mg mL⁻¹, the PEG‐PT@PA brush still exhibits excellent protein resistance (Figure S34), far better than the other polymer brushes (Figure S35).

FIGURE 4.

Frequency (Δf) shifts during hydrogen bonding recognition procedure of PEG‐PT on the PA brush and the subsequent protein resistance test with (a) Lyz and (b) BSA. (c) Re‐writing process with PDMA‐PT after first grafting PEG‐PT and the corresponding protein resistance tests. (d) Re‐writing process with PEG‐PT after first grafting PDMA‐PT and the corresponding protein resistance tests. The protein concentration is 2.0 mg mL⁻¹. (e) QCM‐D characterization on protein capturing and collecting by first grating PAG‐PT on the PA brush. (f‐h) Fluorescence visualizing on the resistance, adsorption, and desorption of protein during one re‐writing process with the PEG‐PT@PA brush and PAG‐PT@PA brush. The pH 10 buffer was selected as the protein recovery agent.

More intriguingly, the rewritable properties of polymer brushes enable us to reversibly switch the surface between protein resistance and protein adsorption. The PEG‐PT@PA brush with good protein resistance to Lyz was converted into the PDMA‐PT@PA brush through the sequential DMF rinse and the grafting of PDMA‐PT (Figure 4c). Likewise, as shown in Figure 4d, the PDMA‐PT@PA brush with weak protein adhesion to Lyz was able to be erased and rewritten into the PEG‐PT@PA brush with good protein resistance properties. Obviously, based on the above procedures, responsive surfaces that allow for switching between protein resistance and protein capture have been achieved. Interestingly, as indicated in Figure S32, Lyz adsorbs on the PA brushes due to the lack of protein resistance capability; Afterward, PEG‐PT brushes are still effectively grafted. This result suggests that the hydrogen bonding recognition between complementary nucleobases can occur atop the adsorbed Lyz, indicating the tolerance of the current grafting strategy to some level of contamination due to the strong specific interactions. In addition, as indicated by the Δf shift, PEG‐PT can be removed in the following DMF rinsing process, while the pre‐adsorbed protein (Lyz) on the PA brush prior to the grafting of PEG‐PT cannot be desorbed.

Capturing or collecting specific proteins with functional surfaces is highly attractive for biomedical research or diagnosis. In order to facilitate the application of rewritable surfaces in biological systems, the effective dissociation of MHBs between the PA brush and PT at pH 10.0 provides an ideal and alternative pathway. Lyz was first captured by the PAG‐PT@PA brush and then released by treating with the buffer of pH 10.0 (Figure 4e). To more clearly showcase the resistance, adsorption, and desorption of protein with the rewritable polymer brushes, fluorescently labeled BSA (FITC‐BSA) was further employed as a model protein. The fluorescence image of the protein on bare Au demonstrates a strong nonspecific adsorption (Figure S36). In stark contrast, the absence of fluorescence signals for the PEG‐PT@PA brush manifests the excellent protein resistance attributed to the PEG brush (Figure 4f). Subsequently, after the treatment of pH 10.0 buffer and the formation of the PAG‐PT@PA brush, massive FITC‐BSA adsorption was observed based on the high fluorescence intensity (Figure 4g). Not surprisingly, after rinsing with pH 10.0 buffer again, fluorescence signal on the surface disappeared (Figure 4h), verifying the detachment of adsorbed FITC‐BSA into the buffer solution. The sequential treatments were conducted three cycles and showed a good rewritable property (Figure S37a–f). Replacing the PAG block with PDMA block led to a similar result (Figure S38). Collectively, the designed MHB recognition system could serve as an attractive platform for bioconcentration, and more specific protein or polypeptide collections can be achieved on surfaces functionalized with customized oligonucleotides.

3. Conclusion

In summary, rewritable polymer brushes based on reversible MHBs between complementary nucleobases were fabricated, enabling the facile modulation of surface properties. Surface RAFT polymerization was employed to prepare nucleobase‐containing polymer brushes, which can be modified with complementary nucleobase‐functionalized diblock copolymers with tailored hydrophilic blocks for properties tunability. The robust yet dynamic MHBs between complementary nucleobases facilitate the efficient rewritability of surface chemical compositions, giving rise to the change of surface properties. This process can be repeated for many cycles without decay, monitored by using in situ QCM‐D, XPS, WCA measurements. More significantly, MHBs of complementary nucleobase‐containing polymers are general and robust methods to construct rewritable surfaces regardless of the chain lengths and chemical compositions of hydrophilic blocks. On this basis, rewritable polymer brushes with thermoresponsive, pH‐responsive, and protein‐resistant properties can be easily engineered and switched at will. Finally, we demonstrate the controlled capturing and releasing of proteins in aqueous solutions, which is promising to achieve the bioconcentration of complex biological samples. Altogether, this work reports a new and novel strategy for modulating surface properties of polymer brushes, holding great applicability in various fields such as biosensing, bioseparation, and photonic crystals.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Supporting File: smll73885‐sup‐0001‐SuppMat.pdf.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.