Standard SEC was performed with THF as the mobile phase (flow rate 1 mL min^‑1) on a SDV column set from PSS (SDV 1000, SDV 100000, SDV 1000000) at 30 °C. Calibration was carried out using PS standards (from Polymer Standard Service, Mainz). For the SEC-MALLS experiments, a system composed of a Waters 515 pump (Waters, Milford, CT), a TSP AS100 autosampler, a Waters column oven, a Waters 486 UV detector operating at 254 nm, a Waters 410 RI-detector and a DAWN DSP light scattering detector (Wyatt Technology, Santa Barbara, CA) was used. For data acquisition and evaluation of the light-scattering experiments, Astra version 4.73 (Wyatt Technology, Santa Barbara, CA) was used. The light-scattering instrument was calibrated using pure toluene, assuming a Rayleigh ratio of 9.78 × 10⁻⁶ cm⁻¹ at 690 nm. An injection volume of 118 μL, a sample concentration of 1–2 g L⁻¹, a column temperature of 35 °C and a THF flow rate of 1 mL min^‑1 have been applied. SEC analysis was performed on a high resolution column set from PSS (SDV 5 μm 106 Å, SDV 5 μm 105 Å, SDV 5 μm 1000 Å). Subsequent slow addition of monomer for the PS latex synthesis was carried out by using a precision piston pump (mikro Prominent). TEM experiments were carried out with a Zeiss EM 10 electron microscope operating at 80 kV. All shown images were recorded with a slow-scan charge-coupled device (CCD) camera obtained from TRS (Tröndle) in bright field mode. Camera control was computer aided using the ImageSP software from TRS. Centrifugation was performed with an Avanti J‑30I from Beckman Coulter for half an hour with a speed of 17,000 rpm. Dynamic light scattering (DLS) experiments were performed with a setup based on a He-Ne laser with a wavelength of λ = 632.8 nm and a goniometer allowing one to measure at scattering angles 2θ from 30° to 160°. Polarization of the primary beam was defined by a Glan-Thomson prism. The scattered beam polarization was again analyzed for its polarization, and all experiments were performed in vertical-vertical geometry. Scattered intensity was detected with an optical fiber coupled to two phototubes. In this way, background could be minimized using the cross-correlated signal from both tubes. The correlation function of intensity was calculated with an ALV 5000 autocorrelator. The sample was filled in a cylindrical cuvette (Hellma) and immersed in a temperature controlled index matching bath. DLS measurements were carried out at 25 °C in THF. The concentrations of the nanoparticle dispersions were approximately 0.01 w% after ultrasonic treatment (3 h for the polymer-grafted particles and 6 h for bare PS particles). After that sonication time, the experimentally obtained value of the hydrodynamic radius, R_h, was constant. The scattering intensity was measured in a range of scattering angles, θ, from 50° to 130°. The autocorrelation function of intensity, g₂(t, q), was thus obtained. SAXS measurements were carried using a custom made system. The scattered intensity was measured as a function of scattering vector q = 4π/λsinθ, where λ is the X-ray wavelength and 2θ the scattering angle. The experimental setup used monochromatized Cu K_α radiation with λ = 1.54 Å, a pinhole collimation and a two-dimensional position sensitive detector by Molecular Metrology. The accessed q-range is from 0.008 Å⁻¹ to 0.25 Å⁻¹. The two-dimensional scattering image from the detector was calibrated using Ag-behenate and radially averaged to calculate the intensity I(q). Samples were measured in borosilicate capillaries with a 1.5 mm diameter, and temperature was controlled with an accuracy of ΔT = 0.2 K. XRD was conducted using a Siemens D500 diffractometer in the reflection mode using an incident X-ray wavelength of 1.54 Å with a scan rate of 0.04° min⁻¹. The diffractometer was equipped with a hot stage to control the temperature of the sample with an accuracy of ΔT = 1 K. The resulting plots of X-ray intensity versus 2θ were analyzed using the profile fitting program. DSC measurements were done on a computer aided TA Instruments DSC Q1000. The sample mass was in the range of 2–4 mg for PDMSB homopolymer, while for PDMSB-grafted PS particles, the mass used was in the range of 12 to 15 mg. Dried N₂ gas was purged with a constant flow rate during the measurement. The temperature reading and caloric measurements were calibrated using indium and blue sapphire as the standard.

All solvents and reagents were purchased from Alfa Aesar, Sigma Aldrich, Fisher Scientific and ABCR and used as received, unless otherwise stated. Tetrahydro-furan (THF), toluene and n-hexane were distilled from sodium/benzophenone under reduced pressure (cryo-transfer) prior to the addition of 1,1-diphenylethylene and n-butyllithium (n-BuLi), followed by a second cryo-transfer. 1,1-dimethysilacyclobutane (DMSB) was dried over CaH₂ and distilled, followed by the addition of 1,1-diphenylethylenelithium (DPHLi), until the red color remained. DMSB was freshly distilled from that solution prior to the anionic ROP. All syntheses were carried out under an atmosphere of nitrogen or argon using the Schlenk technique or a glovebox equipped with a Coldwell apparatus.

Exemplary synthesis for PDMSB with a molar mass of Approx. 30 kg mol⁻¹: In a glovebox, 470 mg DMSB (4.69 mmol) is dissolved in 20 mL of neat THF in an ampoule equipped with a stirring bar. The solution is cooled to −60 °C by using the Coldwell apparatus, and the polymerization is initiated by adding 7 µL n-BuLi (1.6 M, 11.2 µmol). After 1 h, the reaction is terminated with methanol and the solution poured into a 10-fold excess of methanol. The polymer precipitates as a colorless solid, is filtered and dried in vacuo (yield: 454 mg, 97%). Molar mass is determined by using SEC-MALLS (M_n = 31,500, M_w = 32,600, PDI = 1.04).

In a 500 mL three-necked flask equipped with magnetic stirring bar, 105 mL degassed water, 6.30 g styrene, 0.70 g divinylbenzene and 0.1 g sodium dodecylsulfate are added. The mixture is stirred and heated to 75 °C. A solution of 0.175 g sodium peroxodisulfate and 0.035 g sodium dithionite in 5 mL water are added to initiate the batch polymerization. After 30 min, an emulsion of 37.8 g styrene, 4.2 g divinylbenzene, 0.35 g sodium dodecylsulfate and 0.42 g Triton X405 in 86 mL degassed water is added continuously with a precision piston pump (flow rate of 1 mL min⁻¹). After the addition, stirring is continued for 1 h at 75 °C with a stirring rate of 300 rpm. The resulting PS latex was characterized by using TEM, revealing a particle diameter of approximately 230 nm.

PDMSB@PS 1: In an ampoule equipped with a stirring bar, 300 mg of dried cross-linked PS particles are dispersed with 7.5 mL dry toluene by stirring vigorously for 24 h inside a glovebox. 45 µL sec-BuLi (c = 1.3 M, 35 µmol) are added, and the dispersion turns slightly orange. After stirring the dispersion for 1 h at room temperature, it is transferred into an ampoule with cooled THF (−60 °C). After stirring the dispersion for 30 min cooled inside the Coldwell apparatus at −60 °C, 280 mg precooled DMSB (−15 °C) are added. The solution is stirred for 2.5 h at −60 °C. The reaction is terminated with methanol and the particle dispersion centrifuged for 30 min at 15,000 rpm. To get rid of impurities and freely formed PDMSB chains, the particles are dispersed in toluene and again centrifuged. This step is repeated at least five times, followed by drying of the functionalized particles in vacuo.

PDMSB@PS 2: In an ampoule equipped with a stirring bar, 280 mg of dried cross-linked PS particles are dispersed with 7.5 mL dry toluene by stirring vigorously for 24 h inside a glovebox. 20 µL sec-BuLi (c = 1.3 M, 15 µmol) are added, and the dispersion turns slightly orange. After stirring the dispersion for 1 h at room temperature, it is transferred into an ampoule with cooled THF (−60 °C). After stirring the dispersion for 30 min at −60 °C inside the Coldwell apparatus, 280 mg precooled DMSB (−15 °C) are added. The solution is stirred for 2.5 h at −60 °C. The reaction is terminated with methanol and the particle dispersion centrifuged for 30 min at 15,000 rpm. To get rid of impurities and freely formed PDMSB chains, the particles are dispersed in toluene and again centrifuged. This step is repeated at least five times, followed by drying of the functionalized particles in vacuo.

Although anionic ROP of DMSB monomer in THF at low temperatures (−48 °C to −60 °C) (Figure 1) leads to a turbidity after approximately 10 to 15 min after addition of n-BuLi as initiator independently of the intended molar mass, high molar masses up to 60 kg mol⁻¹ could be obtained with low polydispersity values (PDI < 1.15). The results are summarized in Table 1.

From Table 1, it becomes clear that molar masses obtained via conventional SEC with PS standards were slightly lower compared to the absolute molar mass values obtained by using SEC-MALLS. An exemplary monomodal, narrowly distributed SEC-MALLS trace for PDMSB with an average molar mass of approximately 32 kg mol⁻¹ is given in Figure 2. The anionic ROP of DMSB is quite fast, and living chain ends can be thought to be very reactive. However, after a longer reaction time (>1 h) under applied conditions, PDMSB samples showed a significant shoulder in SEC traces shifted to higher molar masses, which can be assumed to be caused by an undesired coupling process of living chain ends with the silane moieties.

For a study of the melting and crystallization behavior of PDMSB homopolymers, samples were heated with a rate of 10 K min⁻¹ to 353 K, and the temperature was kept constant for 10 min to delete thermal history. Then, the sample was cooled to 253 K with a rate of 10 K min⁻¹ to obtain the DSC exotherms, followed by heating again to obtain the DSC endotherms. In Figure 3, the DSC curve of PDMSB with an average molar mass of 5.6 kg mol⁻¹ is exemplarily given.

From Figure 3, it becomes clear that only one crystallization peak in the vicinity of 283 K during the cooling process was apparent. However, subsequent heating showed that there are unambiguously two melting peaks at 295 K and another at 303 K. Similar multiple melting peak phenomena have been reported in studies with low molar mass PEO homopolymers. In those investigations with PEO, the untypical thermal behavior is known as the integral folding (IF) and nonintegral folding (NIF) structure. Kovacs et al. pioneered this issue and studied the relationship between linear growth rate, single crystal morphology and the IF structure [41,42,43,44,45]. Cheng et al. demonstrated the existence of the NIF structure using time resolved small-angle X‑ray scattering (SAXS) [46,47,48,49,50,51,52,53,54,55,56]. At first glance, it seems that a similar mechanism might play a role for low molar mass PDMSB homopolymers, but further investigations are necessary, as described in the following section.

In Figure 4, the X-ray diffraction (XRD) pattern of the PDMSB sample with an average molar mass of 5.6 kg mol⁻¹ is shown, which has been isothermally crystallized at 283 K after annealing at 353 K for 10 min. The scattering pattern consists of a series of narrow Bragg peaks. Obviously, the sample is partially crystalline. The peak positions are the same as those reported previously by Kawahara et al. [34]. Only the relative intensity of the peaks is different. This can be caused by a different orientation of crystallites in the samples as a consequence of the sample preparation procedure.

We now turn to the crystalline/amorphous mesostructure of the sample. Figure 5 shows the Lorentz-corrected SAXS profile for the melt-crystallized sample at 283 K for 120 min. The results show one long range order peak, which relates to a long period of 10.7 nm. This differs from observations in the isothermal crystallization behavior of PEO homopolymers [48]. For PEO, it has been found that at first, a scattering peak was observed during isothermal crystallization, followed by a decrease of the scattering peak, and the appearance of two other scattering peaks developed gradually. Isothermal thickening and/or thinning processes lead to the formation of the final IF chain crystals for low molecular weight PEO, which can be used to explain the multiple melting peaks phenomenon. However, for PDMSB, this is not the case, as only one scattering peak is observed after crystallization.

To sum up, for all results derived by DSC, XRD and SAXS measurements for low molar mass PDMSB homopolymers, we assume that the first melting peak corresponds to crystal lamellae formed during isothermal crystallization, while the second one is caused by recrystallization during the heating process. DSC measurements show that when isothermal crystallization temperature, T_c, is low enough, there will be two melting peaks, but only one melting peak when T_c is high. Recent DSC curves of isothermal crystallized PDMSB samples also show that there is only one peak without any shoulders. This interesting crystallization behavior for low molar mass PDMSB will be explicitly discussed in a prospective work.

Investigations regarding the crystallization of PDMSB homopolymers with higher molar masses show a fast and distinct crystallization, which shows PDMSB to be an excellent candidate for studying the influence of the crystallization of anchored polymers on a curved substrate, as described in the following sections.

As a solid model substrate for the intended surface-initiated anionic polymerization of DMSB and to study the crystallization behavior of surface-attached PDMSB chains, PS nanoparticles were used, which were cross-linked with 10 wt% divinylbenzene. Those particles were used because of their simple synthesis via seeded emulsion polymerization, similar to a previously described procedure, leading to almost monodisperse particles [57]. For further purification, the particles were dried by three-fold azeotropic distillation with dry toluene under high vacuum conditions. To ensure the absence of protic impurities, which would immediately cause a termination of the anionic polymerization, the particle dispersion in toluene was additionally titrated, as described in the following. Therefore, sec-BuLi was slowly added with a µL-syringe, until a slightly yellowish color appeared, which remained for at least 15 min, due to the nucleophilic addition at the accessible vinyl groups in the swollen particles’ shell. In the next step, the calculated amount of initiator for the intended molar masses of PDMSB was added, followed by DMSB monomer addition (Figure 6). The polymerization was terminated with degassed methanol, and surface-grafted particles were purified by repeated centrifugation and redispersing in neat THF for at least five times.