**4. Photoinduced depolymerization of poly(olefin sulfone)s**

A poly(olefin sulfone) possessing a photobase generating group depolymerizes upon photoirradiation and heating (**Figure 7**). Poly(olefin sulfone)s that possess photobase‐generating groups were synthesized (**Figures 8** and **9**) [17]. The photobase‐generating groups produce amine groups when irradiated with light. Photoinduced decomposition of the poly(olefin sulfone) was investigated using 1 H NMR. A poly(olefin sulfone) film was subjected to irradiation with 254‐nm light, after which 1 H NMR spectra were recorded. **Figure 10(a)** and **(b)** show the <sup>1</sup> H NMR spectra of polymer 10 before and after irradiation, respectively, followed by heating. The progress of depolymerization was readily confirmed by the disappearance of the methylene and methine protons in the main chain (4.3–3.8 ppm), along with the appearance of signals near 5.1 and 5.8 ppm, which were assigned to protons on a vinyl group. The decomposition ratio of polymer 10 irradiated and heated under the conditions described above was estimated to be 95%. The decomposition ratio increased with the irradiation energy density (**Figure 11**). Conversion of the polymer to the olefin monomer (depolymerization ratio) was also estimated to be 50%. The irradiated film (polymer 10) after heating was dissolved in THF and the molecular weight measured by gel permeation chromatography (GPC) (**Figure 12**). The polymer completely disappeared and low‐molecular‐weight species appeared. The retention time of the lowest molecular weight species was coincident with that of the olefin monomer. The number average molecular weight decreased from 130,000 to 300.

As shown in **Figure 13**, a lithographic image with clear positive tone of alternating 40‐μm wide lines and gaps on a film of polymer 10 could be developed with 0.012 M aq. HCl.

**Figure 7.** Proposed mechanism of base‐catalyzed thermal depolymerization of 1:1 alternating poly(olefin sulfone)s.

Irradiation with 254‐nm light triggered the generation of a base along with creation of a latent image. The visible image could be developed after heating the exposed polymer film.

to the DEBA monomer. **Figure 6** shows a picture of a concentrated solution of a poly(olefin sulfone). Although the viscosity of the solution was very high, when a trace of triethylamine

A poly(olefin sulfone) possessing a photobase generating group depolymerizes upon photoirradiation and heating (**Figure 7**). Poly(olefin sulfone)s that possess photobase‐generating groups were synthesized (**Figures 8** and **9**) [17]. The photobase‐generating groups produce amine groups when irradiated with light. Photoinduced decomposition of the poly(olefin

by heating. The progress of depolymerization was readily confirmed by the disappearance of the methylene and methine protons in the main chain (4.3–3.8 ppm), along with the appearance of signals near 5.1 and 5.8 ppm, which were assigned to protons on a vinyl group. The decomposition ratio of polymer 10 irradiated and heated under the conditions described above was estimated to be 95%. The decomposition ratio increased with the irradiation energy density (**Figure 11**). Conversion of the polymer to the olefin monomer (depolymerization ratio) was also estimated to be 50%. The irradiated film (polymer 10) after heating was dissolved in THF and the molecular weight measured by gel permeation chromatography (GPC) (**Figure 12**). The polymer completely disappeared and low‐molecular‐weight species appeared. The retention time of the lowest molecular weight species was coincident with that of the olefin monomer. The number average molecular weight decreased from

As shown in **Figure 13**, a lithographic image with clear positive tone of alternating 40‐μm wide lines and gaps on a film of polymer 10 could be developed with 0.012 M aq. HCl.

**Figure 7.** Proposed mechanism of base‐catalyzed thermal depolymerization of 1:1 alternating poly(olefin sulfone)s.

H NMR spectra of polymer 10 before and after irradiation, respectively, followed

H NMR. A poly(olefin sulfone) film was subjected to irra-

H NMR spectra were recorded. **Figure 10(a)** and **(b)**

vapor was added to the solution, the viscosity decreased immediately.

**4. Photoinduced depolymerization of poly(olefin sulfone)s**

sulfone) was investigated using 1

show the <sup>1</sup>

126 Alkenes

130,000 to 300.

diation with 254‐nm light, after which 1

**Figure 8.** Structures of poly(olefin sulfone)s that generates primary amine by photo irradiation and the photochemical reactions of the pendant group.

**Figure 9.** Structures of poly(olefin sulfone)s that generates secondary amine by photo irradiation and the photochemical reactions of the pendant group.

**Figure 10.** <sup>1</sup>

H NMR spectra of polymer 10 in DMSO‐d<sup>6</sup>

followed by heating at 150**°**C for 15 min, and (c) monomer 10.

(a) before UV irradiation, (b) after 254‐nm irradiation of 600 mJ/cm<sup>2</sup>

Poly(olefin sulfone)s

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**Figure 10.** <sup>1</sup> H NMR spectra of polymer 10 in DMSO‐d<sup>6</sup> (a) before UV irradiation, (b) after 254‐nm irradiation of 600 mJ/cm<sup>2</sup> followed by heating at 150**°**C for 15 min, and (c) monomer 10.

**Figure 9.** Structures of poly(olefin sulfone)s that generates secondary amine by photo irradiation and the photochemical

reactions of the pendant group.

128 Alkenes

**Figure 11.** Decomposition ratio of polymer 10 heated at 150**°**C for 15 min after UV irradiation as a function of irradiation energy.

**5. Effect of main chain structure on depolymerization of poly(olefin** 

**Figure 13.** SEM image of polymer 10 film after UV irradiation at 100 mJ/cm<sup>2</sup>

Photoinduced depolymerization of the polymers shown in **Figure 3** mixed with a low‐ molecular‐weight photo‐base generator (ANC2) was investigated [18]. **Figure 14(a)** shows the change in the IR spectrum of PMPS film coated on a KBr plate without light irradiation, and **Figure 14(b)** shows the corresponding spectrum after light irradiation during heating (post‐exposure heat treatment). The absorption spectrum of the nonirradiated film was independent of the heating time, whereas the sulfonyl stretching bands (1311 and 1130 cm−1) decreased with the heating time after film irradiation, which indicates decomposition of the polymer main chain. The extent of decomposition increased with the irradiation energy density (**Figure 14(c)**), and the extent of PMPS decomposition was estimated to be 95%. Conversion of the polymer to the olefin monomer (extent of depolymerization) was estimated

, followed by heating at 130**°**C for 60 sec and

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H NMR as 92%. Therefore, the polymer was converted to monomers with very high efficiency. **Figure 15(a)** shows the residual ratio of the PBS sulfonyl group as a function of heating time after photoirradiation. The change in residual ratio (decomposition of the main‐chain) was slow compared to that for PMPS. In contrast, the change in the residual ratio of PMBS was as fast as that for PMPS (**Figure 15(b)**). The only structural difference between PBS and PMBS is the number of substituents on the main chain. Thus, the decomposition characteristics must be dependent on the structure of the main chain. **Figure 16** shows the residual ratios for all polymers as a function of heating time after photoirradiation. The results show that the decomposition characteristics of the polymers can be divided into two groups: poly(olefin sulfone)s that possess only one type of proton on the main chain (branched 1‐olefins such as PMBS, PMPS, PMHS, and PMNS), and poly(olefin sulfone)s that possess two types of protons

**sulfone)s**

washed with 0.012 M HClaq.

by 1

**Figure 12.** GPC curves of polymer 10 (a) before UV irradiation, (b) after UV irradiation at 600 mJ/cm<sup>2</sup> , followed by heating at 150**°**C for 15 min, and (c) the corresponding olefin monomer.

**Figure 13.** SEM image of polymer 10 film after UV irradiation at 100 mJ/cm<sup>2</sup> , followed by heating at 130**°**C for 60 sec and washed with 0.012 M HClaq.
