Crosslinked CO₂‐Based Polycarbonate: Biobased Pressure‐Sensitive Adhesives Combining Wettability and Cohesive Strength

ABSTRACT

CO₂‐based polycarbonates show great potential for application as biodegradable pressure‐sensitive adhesives (PSAs). However, it remains challenging for polycarbonate‐based PSAs to achieve rapid surface wetting while simultaneously maintaining sufficient cohesive strength. To address this issue and improve adhesive performance, we propose a strategy for preparing crosslinked polycarbonate PSAs. As a proof of concept, bio‐derived epoxides, including furfuryl glycidyl ether and n‐butyl glycidyl ether, were introduced as key monomers to synthesize functionalized CO₂‐based polycarbonates (PBFCs). The crosslinked PSAs were subsequently constructed through a Diels–Alder reaction, while the flexible side chains enabled rapid wetting of the adhesive on the substrate surface. As a result, the static shear adhesion was significantly improved from approximately 0.1 h to over 24 h, accompanied by a tack grade of #2. Notably, the prepared PSAs could be reused for three cycles while maintaining a peel strength of approximately 2 N cm⁻¹, and no visible residue was observed on the substrate after peeling. This study develops a series of crosslinked CO₂‐based PSAs from bio‐based epoxides, providing a promising platform for the design of high‐performance biodegradable PSAs.

CO₂‐based polycarbonates demonstrate significant potential in the application of biodegradable pressure‐sensitive adhesives (PSAs). However, achieving rapid surface wetting while maintaining sufficient cohesive strength remains a challenge for linear polycarbonates. To address these issues and enhance PSA performance, this study proposes a strategy for preparing crosslinked CO₂‐based polycarbonate PSAs. Polycarbonates (PBFC) were synthesized via the copolymerization of bio‐based glycidyl ethers (furfuryl glycidyl ether and n‐butyl glycidyl ether) with carbon dioxide. Subsequently, the furan rings on the side chains of PBFCs reacted with bismaleimide hexane via Diels–Alder chemistry to form crosslinked PSAs, whereas the flexible side chains of PBFC facilitated rapid wetting of the substrate surface. Results demonstrated that the introduction of the crosslinked structure significantly enhanced the static shear adhesion force (increasing from approximately 0.1 h to over 24 h). Notably, the prepared PSAs could be reused three times while maintaining a peel strength of approximately 2 N/cm, with no residues observed on the substrate during peel tests. In this study, a series of crosslinked CO₂‐based PSAs were developed using bio‐based epoxides, providing a novel platform for the production of high‐performance biodegradable PSAs.

1. Introduction

Adhesives are widely used in many fields of human life, including office supplies, construction, automotive, electronics, healthcare, and other industries. To achieve adhesion, adhesives generally require stimulation factors such as heat, light, pressure, and water [1]. Among them, pressure‐sensitive adhesives (PSAs) can achieve adhesion under finger pressure. They are widely used in daily life, such as in films, labels, and tapes, as well as in high‐value applications, such as medical dressings and transdermal patches. Generally, commercial PSAs were constructed with acrylic, rubber, silicone, and polyurethane structures, but the carbon–carbon main chain structure makes them difficult to degrade naturally. Meanwhile, PSAs are difficult to recycle on a large scale like plastics. These drawbacks have caused significant environmental impacts after product disposal. Therefore, the development of degradable PSAs is of great significance for achieving sustainable development, which has attracted the attention of researchers worldwide [2, 3].

Polycarbonates prepared through the copolymerization of carbon dioxide and epoxides have shown great potential as biodegradable PSAs [4, 5, 6, 7, 8, 9, 10, 11, 12]. Their degradable potential is mainly associated with the aliphatic polycarbonate backbone, in which carbonate linkages are more susceptible to hydrolysis and biological erosion than conventional carbon–carbon backbones. For example, Grinstaff and coworkers reported glycidyl ester/CO₂‐derived polycarbonate PSAs with peel adhesion comparable to that of commercial tapes, and these materials could degrade into benign products such as glycerol, alcohols, and CO₂ [13, 14, 15]. Lee et al. also demonstrated the biodegradation of PPC‐based polymers under natural soil and industrial composting conditions and identified degradation‐related microorganisms by metagenomic analysis [16]. These studies provide literature support for the degradability of CO₂/epoxide‐derived aliphatic polycarbonates. Recently, Wang et al. developed a series of high‐molecular‐weight (30–220 kg/mol), low‐carbonate‐content (30%, 40%, and 50%) CO₂‐based poly(carbonate‐ether) PSAs through the copolymerization of CO₂ and propylene oxide. By comprehensively regulating the molecular weight and carbonate unit content of the poly(carbonate‐ether)s, the viscoelastic properties of the PSAs could be effectively tuned [17, 18]. These CO₂‐based polycarbonates have expanded the structural diversity and properties of biodegradable PSAs. However, their adhesive performance still lags behind that of commercial PSAs, mainly because it is difficult to achieve rapid surface wetting and sufficient cohesive strength at the same time. Since crosslinking is an effective strategy to improve cohesive strength in commercial PSAs [19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31], developing crosslinked polycarbonates is expected to further enhance the performance of biodegradable PSAs.

Herein, a strategy to prepare crosslinked polycarbonate was proposed to enhance the adhesion performance of degradable PSAs. As a proof of concept, furfuryl glycidyl ether (FGE) and n‐butyl glycidyl ether (BGE), respectively derived from bio‐based furfuryl alcohol and n‐butanol, were introduced as key monomers to produce functionalized CO₂‐based polycarbonate (PBFC) (Scheme 1). BGE provides flexible side chains for chain mobility and surface wetting, whereas FGE introduces furan groups for Diels–Alder crosslinking with bismaleimide. By tuning the BGE/FGE feed ratio and the maleimide/furan ratio, the viscoelasticity and adhesive properties of the resulting PSAs can be regulated, providing a new platform for high‐performance degradable CO₂‐based PSAs.

SCHEME 1.

The strategy to prepare crosslinked CO₂‐based polycarbonate using bio‐derived epoxides to enhance the adhesion performance of degradable PSAs.

2. Experimental Section

2.1. Materials

Furfuryl alcohol (FA, 98%), n‐butanol alcohol (n‐BA, 98%), 1,6‐hexamethylenediamine (98%), and epichlorohydrin (ECH, 98%) were purchased from Shanghai McLean Biochemical Technology Co., Ltd. Tetrabutylammonium bromide (TBAB, 98%) was provided by Aladdin Industrial Corp. (Shanghai, China). Except for BGE, which uses calcium hydride to remove water and adds molecular sieves for protection, all chemical reagents are used directly.

2.2. Synthesis of Furfuryl Glycidyl Ether (FGE) [32]

51 g (0.55 mol) of ECH and 3.8 g of TBAB were charged into a 250 mL three‐necked round‐bottom flask equipped with a magnetic stir bar. When the solution was maintained at 25°C with a water bath, 49 g (0.5 mol) of FA was added dropwise in 30 min. The reaction mixture was stirred for 2 h at room temperature. After that, 80 mL of sodium hydroxide aqueous solution (50 wt%) was added dropwise within 1 h. After the dropwise addition was completed, the reaction was continued for another 2 h. Afterward, the organic phase was extracted using 100 mL of dichloromethane, washed three times with 50 mL of deionized water, dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by a rotary evaporator to obtain a light‐yellow liquid. The colorless liquid product was obtained after distillation of the crude product at 103°C−105°C in a vacuum (11 mmHg) (62 g, 80% yield). ¹H NMR (500 MHz, CDCl₃): δ7.44–7.39 (m, ¹H), 6.38–6.31 (m, 2H), 4.53 (q, J = 12.8 Hz, 2H), 3.75 (J = 11.5, 3.1 Hz, ¹H), 3.44 (J = 11.5, 5.8 Hz, ¹H), 3.16 (J = 5.8, 4.0, 2.9 Hz, ¹H), 2.80 (J = 9.2, 4.4 Hz, ¹H), 2.61 (J = 5.0, 2.7 Hz, ¹H) (Figure S1). ¹³C NMR (100 MHz, DMSO‑d₆): δ 151.88, 143.63, 110.89, 110.07, 70.91, 64.50, 50.63, and 43.87 (Figure S2). The BGE synthesis method is similar to the FGE. (Figures S3∼S4).

2.3. Synthesis of Bis(Maleimido)Hexane(BMIH) [33]

10.79 g (0.11 mol) of maleic anhydride was dissolved in 30 mL of DMF. Then, 5.81 g (0.05 mol) of hexanediamine dissolved in 6 mL of DMF was slowly added through a constant pressure dropping funnel and reacted at 60°C for 1 h. After, acetic anhydride (12.3 g, 0.12 mol) was added, followed by sodium carbonate (0.2 g, anhydrous). Mixture products were allowed to stir overnight at 60°C, after which it was cooled to room temperature, precipitated, washed with ice‐cold water, and dried in a vacuum. Purify it with column chromatography on silica (Hexane: EtOAc = 2:1) to afford the product. (4.83 g, 35% yield). ¹H NMR (500 MHz, CDCl₃): δ 6.68 (s, 4H), 3.52–3.46 (m, 4H), 1.57 (dd, J = 13.0, 6.2 Hz, 4H), 1.33–1.24 (m, 4H) (Figure S5). ¹³C NMR (400 MHz, CDCl₃) δ 170.85, 134.05, 37.70, 28.35, and 26.18 (Figure S6).

2.4. Synthesis of PBFC

FGE, BGE, catalyst SalenCo, and auxiliary catalyst PPNTFA were added to the reaction vessel. The carbon dioxide pressure was maintained at 4 MPa. The reaction was carried out in a 30°C water bath for 24 h. The ratio of the epoxide to the catalyst and auxiliary catalyst was always kept at 500:1:1.

2.5. Preparation of Uncrosslinked PSAs

The preparation of PSA tape is in accordance with the Chinese national standard GB/T 2792‐2014. The PBFC is dissolved in dichloromethane to form a 0.2 g/mL solution. The solution is evenly coated on the surface of the PET film using a wire rod coating device, and then it is placed in a fume hood to stand in a dust‐free environment for 12 h. Then, the PET release film coated with silicone oil is covered on the polymer, and it is cut into a 24 mm × 297 mm PSA strip.

2.6. D–A Reaction to Prepare Crosslinked PSAs

The PBFC is dissolved in dichloromethane to form a 0.2 g/mL solution. Then, BMIH is added, and the solution is evenly coated on the surface of the PET film using a wire rod coating device, and then it is placed in a fume hood to stand in a dust‐free environment for 12 h. The reaction is carried out at 60°C for 2 h, and finally, the PSA strip is prepared.

3. Results and Discussion

3.1. Design and Preparation of CO₂‐Based Polycarbonate

PSAs are typical viscoelastic materials that achieve adhesion mainly through intermolecular interactions rather than chemical bonding with the substrate surface. Therefore, their performance requires a balance between sufficient chain mobility for rapid wetting and adequate cohesive strength for durable adhesion [34]. In this work, BGE and FGE were selected to play complementary roles in CO₂‐based polycarbonate PSAs. BGE introduces flexible n‐butyl ether side chains, which lower the glass transition temperature (T_g ), enhance segmental mobility, and promote deformation and surface wetting under light pressure, thereby improving tack. In contrast, FGE introduces furan‐containing side groups as reactive sites for subsequent Diels–Alder crosslinking. A low FGE content preserves chain flexibility while providing crosslinkable sites, whereas excessive FGE increases chain rigidity and weakens wetting. After reaction with BMIH, the furan groups form covalent crosslinking junctions that restrict long‐range chain slippage and improve cohesive strength. Thus, BGE mainly contributes to chain mobility, wetting, and tack, whereas FGE determines the crosslinking capability and final cohesive strength of the PSA network.

The designed glycidyl ether monomers, including FGE and BGE, were synthesized through the reaction of epichlorohydrin with bio‐based alcohols, namely furfuryl alcohol and n‐butanol, respectively. After monomer preparation, a series of CO₂‐based polycarbonates were synthesized through the terpolymerization of CO₂, BGE, and FGE. SalenCo was selected as the catalyst to ensure a sufficient carbonate‐unit content in the polymer chains, which is crucial for degradability. All the obtained polycarbonates were characterized by ¹H NMR spectroscopy and size exclusion chromatography (SEC) (Figures S7–S12). As shown in (Figure 1), the characteristic signals of the epoxide groups at 3.3–2.5 ppm in the monomers (Figure 1a,b) disappeared after polymerization, while new signals corresponding to the polycarbonate backbone appeared at approximately 5.0 ppm. In addition, the signals at 1.7–0.8 ppm are attributed to the butyl protons of the BGE units, whereas the peaks at 6.3 and 7.4 ppm correspond to the furan ring protons of the FGE units. These results confirm the successful formation of polycarbonates through CO₂/BGE/FGE terpolymerization. Furthermore, the composition of BGE and FGE units in the polycarbonates could be readily controlled by varying the monomer feed molar ratio (Table 1). To investigate the effect of crosslinking density on PSA properties, a series of polycarbonates with FGE unit contents of 0% (P₀), 5% (P_0.05), 10% (P_0.1), 20% (P_0.2), and 50% (P_0.5) were prepared. Thermogravimetric analysis (TGA) results (Figure 2a) showed that all the prepared polycarbonates exhibited 5% weight‐loss decomposition temperatures (T _{d,5 wt%}) above 200°C, which is sufficient to meet the requirements of general PSA applications.

FIGURE 1.

¹H NMR spectra (500 MHz, CDCl₃) of (a) FGE, (b) BGE, and (c) P_0.2.

TABLE 1.

PBFC is synthesized by the ring‐opening copolymerization of CO₂, BGE, and FGE.

En.	Epoxides: Cat: PPNTFA	Time (h)	f (FGE) a	F (FGE) b	Conv. c (%)	Selec. d (%)	M n, theory (kg/mol)	M n, GPC e (kg/mol)	PDI e
1	500:1:1	24	0	0	71.1	92.6	57.3	15.8	1.07
2	500:1:1	24	0.05	0.06	80.9	90.9	72.3	18.9	1.12
3	500:1:1	24	0.1	0.11	89.3	91.7	80.0	23.1	1.10
4	500:1:1	24	0.2	0.2	94	90.9	82.5	22.0	1.13
5	500:1:1	24	0.5	0.48	94.9	89.3	79.0	22.3	1.20

^a The proportion of FGE in the beginning and the f = x/(x+y).

^bThe proportion of FGE in the clean polymer and the F = n/(m+n).

^cThe conversion of epoxides to polycarbonate and cyclic carbonate was determined through ¹H NMR characterization, and the conversion of epoxides = (A_{5.0 ppm}+ A_{4.8 ppm∼4.7 ppm})/(A_{5.0 ppm}+ A_{4.8 ppm∼4.7ppm}+ A_2.8 ppm).

^dThe selectivity of polymer over cyclic carbonate, and polymeric selectivity = (A_5.0 ppm)/(A_{5.0 ppm}+ A_{4.8 ppm∼4.7 ppm}).

^eThe polydispersity index (PDI) was determined by gel permeation chromatography in DCM at 35°C calibrated against polystyrene standard.

FIGURE 2.

The partial performance characterization of PBFC. (a) The TGA curves of PBFC. (b) Differential scanning calorimetry (DSC) curves of PBFC. The storage modulus, loss modulus, and complex viscosity of P₀ (c), P_0.05 (d), P_0.1 (e), P_0.2 (f), and P_0.5 (g) under dynamic frequency from 0.01 to 100 Hz. (h) The tack and static shear adhesion of PBFC and the commercial tapes. (i) The 180° peel strength test of PBFC and the commercial tapes.

3.2. The Adhesive Properties of Uncrosslinked Polycarbonate

The adhesion process of PSAs involves viscous flow under slow and gentle pressure, accompanied by effective surface wetting. To generate intermolecular interactions and ensure sufficient interfacial adhesion, PSAs must approach the substrate surface within a critical distance of approximately 5 × 10⁻¹⁰ m through efficient wetting [35, 36, 37]. Therefore, adequate chain flexibility during adhesion is essential for PSA performance. In general, the T_g of PSAs should be 30°C–70°C lower than the service temperature, which is typically room temperature. As shown in (Figure 2b), the T_g values of PBFCs are suitable for their application as PSAs. When the FGE unit content was below 20%, its influence on the polymer T_g was negligible, with T_g values mainly ranging from −30°C to −20°C. A noticeable increase in T_g to approximately −10°C was observed only when the FGE unit content reached 50%. This phenomenon can be attributed to the bulky furan groups, which partially restrict the mobility of polymer chains. Overall, the introduction of a small amount of FGE units (< 20%) as crosslinking sites does not significantly compromise the flexibility of the polymer chains.

Compared with DSC measurements, rheological testing can more directly reflect the ability of polymers to deform and wet the substrate surface. Generally, in the low‐frequency region at the service temperature of PSAs, typically 25°C, the storage modulus should be lower than 3.3 × 10⁵ Pa according to the Dahlquist criterion [38]. As shown in (Figure 2c–g), dynamic rheological tests performed over a frequency range of 0.01–100 Hz demonstrate that the modulus values of PBFC satisfy the Dahlquist criterion. However, it is noteworthy that in the low‐frequency region, the loss modulus of PBFC is much higher than its storage modulus. This result suggests that PBFC behaves more like a liquid than a solid during adhesion under low‐frequency deformation [39]. This observation is consistent with the practical behavior of PBFC, which can flow under gravity (Figure S13). These results indicate that the polycarbonates prepared in this study possess excellent chain flexibility, enabling rapid wetting of the substrate surface.

In addition to good wetting ability, sufficient cohesive strength is also essential for PSAs to achieve high shear resistance and avoid cohesive failure. Therefore, after bonding, the adhesive layer should exhibit solid‐like behavior. As shown in (Figure 2h), the tack, evaluated using the rolling ball method, and static shear adhesion of the prepared PBFC samples were compared with those of two commercial tapes from Nitto and Scotch. The results show that although the tack values of P₀ (#4) and P_0.05 (#4) are comparable to those of the commercial tapes (#5 and #4), their static shear adhesion is significantly lower, with a value of only approximately 0.1 h. This difference can be attributed to insufficient intermolecular interactions between polymer chains, resulting in inadequate cohesive strength. In addition, peel adhesion tests (Figure 2i) show that most of the prepared PBFC samples, except P₀, exhibit higher peel adhesion values of 2.45–3.53 N cm⁻¹ than the commercial tapes, which show a peel adhesion of 2.16 N cm⁻¹. However, cohesive failure occurred for all PBFC tapes during peel testing, as evidenced by polymer residue remaining on the substrate after tape removal, which is undesirable for practical applications (Figure S14). Therefore, although the prepared PBFC exhibits good wetting ability, its cohesive strength remains insufficient for practical use. These results demonstrate that the introduction of a crosslinked structure is crucial for improving the performance of CO₂‐based PSAs.

3.3. Adhesive Properties of Crosslinked Polycarbonate

To construct the crosslinked structure, a D–A reaction was carried out between the furan groups anchored on the side chains of PBFC and maleimide‐functional crosslinkers, such as BMIH, as illustrated in Figure 3a. Owing to its balanced tack and peel adhesion, P_0.05 was selected for further investigation. Fourier transform infrared (FT‐IR) spectroscopy was employed to monitor the D–A reaction, and the spectra of BMIH, P_0.05, and the D–A reaction product are shown in Figure 3b. The characteristic peak at 1745 cm⁻¹ is assigned to the carbonate carbonyl groups in the PBFC backbone, while the maleimide carbonyl peak of BMIH appears at 1689 cm⁻¹. After the D–A reaction, the disruption of the conjugated maleimide structure leads to a characteristic shift of this peak to 1701 cm⁻¹. This spectral change confirms the successful occurrence of the D–A reaction. To investigate the effect of crosslinking density, maleimide groups were introduced at molar ratios of 1/5, 2/5, 1/2, 3/5, 4/5, and 5/5 relative to the furan groups. The resulting crosslinked PSAs were denoted as P_0.05%–1%, P_0.05%–2%, P_0.05‐2.5%, P_0.05%–3%, P_0.05%–4%, and P_0.05%–5%, corresponding to 1%–5% of the PBFC structural units, respectively.

FIGURE 3.

a) Diels−Alder reaction of PBFC with BMIH. b) FT‐IR spectra of BMIH, P_0.05 before and after D–A reaction.

Figure 4a compares the tack and static shear adhesion of PSAs with different crosslinking degrees with those of two commercial tapes. The results show that the static shear adhesion of P_0.05 was markedly enhanced from only a few minutes to over 24 h after crosslinking. In contrast, the peel adhesion showed no obvious decrease after crosslinking, remaining in the range of 2.62–5.28 N cm⁻¹ (Figure 4b). This result may be attributed to the fact that the introduction of crosslinked structures mainly improves the cohesive strength of PSAs, whereas peel strength is primarily governed by the interfacial interactions between the adhesive and the substrate.

FIGURE 4.

The influence of crosslinking on PBFC. (a) The tack and static shear adhesion of P_0.05‐x and the commercial tapes. (b) The 180° peel strength test of P_0.05‐x and the commercial tapes. (c) The storage modulus, loss modulus, and complex viscosity of P_0.05%–2% under dynamic frequency from 0.01 to 100 Hz. (d) The residual result of P_0.05%–1% and P_0.05%–2% on the substrate after the peel test. (e) The influence of the number of repeated uses on the 180° peel strength of P_0.05%–2%. (f) The 180° peel strength test of P_0.05%–2% on different substrates.

The remarkable improvement in static shear adhesion can be further understood from the creep behavior of PSAs under sustained loading. For uncrosslinked PBFC, the low‐frequency rheological results show that the loss modulus is higher than the storage modulus, indicating that viscous flow dominates during long‐time deformation. Under a constant shear load, the polymer chains can therefore undergo long‐range slippage and gradually accumulate irreversible deformation, which finally leads to cohesive failure and adhesive residue on the substrate. After the D–A reaction with BMIH, covalent junctions are introduced between PBFC chains. These network junctions increase the elastic contribution of the adhesive layer, prolong the relaxation time, and restrict terminal flow of the chains. As a result, the applied shear stress can be partially stored and resisted by the elastic network instead of being completely dissipated through viscous flow, thereby suppressing creep deformation and improving static shear adhesion from approximately 0.1 h to over 24 h.

Dynamic mechanical analysis further supports this interpretation. For the optimized P_0.05%–2% sample, the storage modulus increased significantly after crosslinking, while tan δ, defined as the ratio of loss modulus to storage modulus, remained close to 1 across the tested frequency range (Figure 4c). Such a balanced viscoelastic state is beneficial for PSAs because sufficient viscous flow is required for surface wetting, whereas adequate elastic resistance is required to prevent chain slippage and cohesive failure. In comparison, insufficient crosslinking in P_0.05%–1% resulted in liquid‐like behavior with tan δ > 1 (Figure S15), indicating that the sparse network was not strong enough to effectively resist creep under sustained loading. Conversely, excessive crosslinking in P_0.05‐2.5% to P_0.05%–5% led to tan δ < 1 (Figures S17–S20), suggesting restricted chain deformability and reduced wetting ability, which caused the tack grade to decrease from #2 to #0. Therefore, P_0.05%–2% represents the optimal crosslinking density in this system, achieving the best balance between interfacial wetting and cohesive strength.

These results also provide a practical formulation guideline for selecting the BGE/FGE feed ratio and the maleimide/furan crosslinking ratio. For applications requiring high tack and rapid wetting, such as temporary labels or easily attachable tapes, a higher BGE content, lower FGE content, and lower crosslinking density are preferred to maintain chain mobility. For applications requiring high shear resistance and cleaner removal, such as removable tapes or residue‐sensitive substrates, an appropriate FGE content and an intermediate crosslinking density should be selected to generate sufficient network strength without sacrificing wetting. In the present system, P_0.05%–2%, corresponding to a low FGE content and a maleimide/furan molar ratio of 2/5, represents a balanced formulation with tack grade #2, stable peel adhesion, static shear adhesion over 24 h, and clean detachment behavior.

After investigating the effect of adhesive structure on performance, further adhesion tests were conducted using the optimized sample, P_0.05%–2%. Owing to its sufficient cohesive strength, P_0.05%–2% exhibited only adhesive failure during peeling, with no visible adhesive residue remaining on the substrate surface. In contrast, cohesive failure was still observed for P_0.05%–1% (Figure 4d). SEM analysis further supported this conclusion: obvious polymer residue patches were observed on the substrate surface after peeling P_0.05%–1%, whereas the substrate surface after peeling P_0.05%–2% appeared much cleaner and more uniform at the observed magnification (Figure S21). As shown in Figure 4e, P_0.05%–2% maintained a peel adhesion of approximately 2 N cm⁻¹ even after three repeated adhesion–peeling cycles, indicating its potential for repeated use as a PSA. The results of additional adhesion–peeling cycles are shown in Figure S22. In addition, to further explore the application scope of P_0.05%–2%, its peel adhesion was evaluated on various substrates. As shown in Figure 4f, P_0.05%–2% exhibited strong peel adhesion of over 2 N cm⁻¹ on most substrates, while showing negligible adhesion on PP and PE substrates. The poor adhesion to PP and PE can be attributed to their low surface energies, which hinder effective surface wetting by P_0.05%–2%. Overall, the introduction of a crosslinked structure effectively reduced adhesive residue during peeling and endowed the resulting PSA, P_0.05%–2%, with reusability after removal.

Despite these promising results, several limitations remain. The peel strength gradually decreased during extended adhesion–peeling cycles beyond the initial reuse tests, and adhesion to low‐surface‐energy substrates such as PP and PE remained weak. In addition, standardized biodegradation data for PBFC are not yet available. To preliminarily assess the environmental stability of the optimized PSA, UV‐aging tests were performed on P_0.05%–2% under a 45 W UV lamp. As shown in Figure S23, the peel force progressively decreased after 6, 12, and 24 h of irradiation, and only weak adhesion remained after 24 h, indicating limited long‐term UV resistance. Therefore, future work should focus on improving resistance to repeated use and UV exposure, enhancing adhesion to low‐surface‐energy substrates, and systematically evaluating degradation behavior under standardized composting, soil, and enzymatic conditions.

4. Conclusion

This study developed D–A crosslinked CO₂‐based polycarbonate PSAs by combining flexible side‐chain design with covalent network formation. Bio‐derived BGE and FGE were copolymerized with CO₂ to prepare furan‐functionalized PBFCs. BGE introduced flexible n‐butyl ether side chains to promote chain mobility and surface wetting, whereas FGE provided furan groups for subsequent crosslinking with BMIH. By tuning the BGE/FGE feed ratio and the maleimide/furan crosslinking ratio, the viscoelastic behavior and adhesive properties of the resulting PSAs could be systematically regulated. The optimized formulation, P_0.05%–2%, exhibited balanced adhesive performance, including a static shear adhesion of over 24 h, a tack grade of #2, and a 180° peel strength of 4.66 N cm⁻¹. The crosslinked network effectively enhanced cohesive strength, suppressed creep deformation, and reduced visible residue during peeling. Moreover, P_0.05%–2% retained a peel strength of approximately 2 N cm⁻¹ after three repeated adhesion–peeling cycles, demonstrating short‐term reusability. Overall, the strategy proposed herein not only provides a new route to bio‐derived CO₂‐based PSAs but also offers a promising platform for improving the comprehensive performance of degradable adhesive systems.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

General chemicals and characterizations; NMR spectra (Figure S1∼ Figure S11); SEC curves (Figure S12); The deformability of PBFC (Figure S13); Cohesive failure of crosslinked polycarbonate PSAs (Figure S14); Rheology test (Figure S15∼Figure S20); SEM images of substrate surfaces after peeling (Figure S21); repeated adhesion–peeling cycles of P_0.05%–2% (Figure S22); UV‐aging test of P0.05%–2% (Figure S23).

Supporting File 1: asia70944‐sup‐0001‐SuppMat.docx

Data Availability Statement

The data that supports the findings of this study are available in the Supporting Information of this article.