Hyperbranched polymers with step-growth chemistries from transfer-dominated branching radical telomerisation (TBRT) of divinyl monomers.

The commercially relevant synthesis of novel materials with step-growth backbones has been achieved by applying conventional chemistries to the radical telomerisation of divinyl monomers leading to high molecular weight branched polymers.

was purchased from Alfa Aesar. All materials were used as received unless otherwise stated.

Nuclear magnetic resonance (NMR) spectroscopy
1 H and 13 C experiments were recorded on a Bruker AMX-400 MHz spectrometer. Samples were analysed in deuterated chloroform (CDCl 3 ) at room temperature. Chemical shifts (δ) are reported in parts per million (ppm) relative to the known solvent residual peak (δ = 7.26 ppm). 13 C, 1 H-HSQC (Heteronuclear Signal-Quantum Coherence), Attached Proton Test (APT) and Distortion Enhanced Polarisation Transfer using 135 decoupler pulse  were also performed at 50 mg/mL. Diffusion Ordered Spectroscopy (DOSY) was performed on kinetic samples in CDCl 3. The standard Bruker double stimulated echo pulse program, with 3 spoil gradients for convection compensation was implemented. Gradient pulse (small delta, ) was set for each sample separately between 900-1300 s, diffusion time (big delta, ) was set for each sample separately between 0.20-0.25 s. DOSY experiments were run in pseudo 2D mode with a linear sequence of 16 steps with gradients strengths from 5 to 95 %. Collected spectra were processed by TopSpin 3.1 software supplied by Bruker. Diffusion coefficients for resolved 1 H signals were extracted from decay curves using the T1/T2 analyse module of the TopSpin program.

Triple Detection Size Exclusion Chromatography (TD-SEC)
All TD-SEC analysis of branched polymers were performed using a Malvern Viscotek instrument using GPCmax VE2001 autosampler, two Viscotek T6000M columns (and a guard column), a refractive index (RI) detector VE3580 and a 270 Dual Detector (light scattering and viscometer) with a mobile phase of THF containing 2 v/v % of triethylamine at 35 °C and a flow-rate of 1 mL/min. All samples were dissolved at 10 mg/mL in the eluent and passed through a 200 nm syringe filter prior to injection (100 µL). From TD-SEC results, M n , M w , Ð, molecular weight distribution and intrinsic viscosity of the polymers were estimated using the Omnisec 5.12 software. Narrow and broad polystyrene standards (Viscotek, Mw = 105 kg/mol, Ð = 1.022 and Mw = 245 kg/mol, Ð = 2.272 respectively) were used to calibrate the instrument.
All SEC analysis of telomers and oligomers were performed using a Malvern Viscotek TDA302 instrument using GPCmax VE2001 autosampler, two Viscotek T2500 columns (and a guard column) and a refractive index (RI) detector (the Dual Detector light scattering and viscometer-fitted on the instrument was not used for the calculation) with a mobile phase of THF at 35 ⁰C and a flow-rate of 0.7 mL/min. All samples were dissolved at 10 mg/mL in the eluent and passed through a 200 nm syringe filter prior to injection (100 µL). Pure DDT was injected as the lowest molecular weight reference with a known value (202 g/mol). The molecular weights of the telomers and oligomers were determined by incrementing the molecular weight of DDT by multiples of 100 g/mol (i.e. molecular weight of MMA).
Polynomial curve fits (OriginPro 2015 software) were implemented and the best fit (r 2 = 0.9999) was found for a cubic function. No species were detected before a retention time of approximatively 15 minutes; the extrapolation of the cubic curve fit function to a 15 minute retention time point clearly shows that the materials formed exhibited MW < 2500 g/mol (Supplementary Figure 35), confirming MALDI and DOSY observations. The RI traces were deconvoluted using Gram-Charlier peak functions (OriginPro 2015 software) and the mass fraction of each identified species derived from the area of the deconvoluted peaks.

Matrix-Assisted Laser Desorption Ionisation -Time of flight (MALDI-TOF)
Mass spectra of linear species formed under specific telomerisation conditions (telomers and oligomers) were analysed using a Bruker Autoflex Mass Spectrometer (Materials Innovation Factory, Liverpool, UK). Spectra for samples containing MMA were the sum of 500 shots acquired in positive-reflectron mode. Cesium triiodide (CsI 3 ) and α-cyano-4hyrdroxycinnamic acid (HCCA) were used as the mass scale calibrant and matrix, respectively.
Samples were prepared at 10 mg/mL in THF. The matrix was dissolved in THF (10 mg/mL).
The solutions were combined at a 5:1 volume ratio of matrix to sample. 2 L of the obtained solution were deposited onto the stainless-steel sample plate and air dried. Spectra for the degradation of p(BDME) were the sum of 500 shots acquired in negative-reflectron mode.
Cesium triiodide (CsI 3 ) and 4-Nitroaniline (4-NA) were used as the mass scale calibrant and matrix, respectively. Samples were prepared at 10 mg/mL in THF. The matrix was dissolved in THF (10 mg/mL). The solutions were combined at a 5:1 volume ratio of matrix to sample.
2 L of the obtained solution were deposited onto the stainless-steel sample plate and air dried.

Elemental microanalysis
CHNS elemental analysis was recorded using a Vario Micro cube

Fourier-transform infrared (FT-IR)
All polymer samples were characterised using a Vertex 70 FT-IR spectrometer fitted with A225/Q platinum ATR and diamond crystal. Transmittance spectra were obtained at 16 scans/spectrum in the region from 4000 cm -1 to 400 cm -1 at a resolution of 4 cm -1 using a deuterated triglycine sulfate and/or mercury cadmium telluride detector.
Toluene was added (50 wt% based on EGDMA and DDT; 2.36 g, 2.73 mL) and the solution stirred and deoxygenated using a nitrogen purge for 15 minutes. The solution was stirred and left to telomerise at 70 °C for 24 hours. The reaction was terminated by exposure to air and cooled. The solution was precipitated into methanol (1:10 ratio) at room temperature affording a white precipitate. After drying the precipitated sample overnight under high vacuum. A sample of the product was taken for 1 H NMR spectroscopic analysis in CDCl 3 and for TD-SEC analysis in THF.

Kinetic analysis through DOSY NMR
In a kinetic study, EGDMA (5 g, 25.2 mmol, 1 equiv.), DDT (6.81 g, 33.6 mmol, 1.33 equiv.), AIBN (0.124 g, 0.756 mmol) were placed into a 50 mL round-bottomed flask. Ethyl acetate was added (50 wt% based on EGDMA and DDT; 11.8 g, 13.1 mL) and the solution stirred and deoxygenated using a nitrogen purge for 15 minutes. The solution was stirred and left to telomerise at 70 °C for 24 hours. To determine the kinetics of the reaction, samples ( 3 mL) were taken at regular intervals and analysed by DOSY NMR. The reaction was terminated by exposure to air and cooled.
Ethyl acetate was added (50 wt% based on EGDMA and DDT; 28.5 g, 31.6 mL) and the solution stirred and deoxygenated using a nitrogen purge for 15 minutes. The solution was stirred and left to telomerise at 70 °C for 24 hours. To determine the kinetics of the reaction, samples ( 3 mL) were taken at regular intervals and analysed by 1 H NMR and SEC. The reaction was terminated by exposure to air and cooled. The solution was precipitated into methanol (1:10 ratio) at room temperature affording a white precipitate. After drying the precipitated sample overnight under high vacuum. A sample of the product was taken for 1 H NMR spectroscopic analysis in CDCl 3 and for TD-SEC analysis in THF.  Table 9.

Entry Time (hrs)
Vinyl Conversion (%) a Mw (g mol -1 ) Mn (g mol -1 ) Ð α dn/dc 1 0 0 n/a n/a n/a n/a n/a  Table 9. Large narrow peak on the right hand-side corresponds to free DDT.