{{ ::cylindrical_specimen_synthesizing.pdf |}}

**1.Purpose:**

The purpose of this protocol is to offer a guideline for synthesizing cylindrical specimens of SMPs, which are suitable for standard uniaxial compression experiments.

**2. Materials and Equipment:**

tert-Butyl Acrylate, Poly(ethylene glycol) Dimethacrylate, Di(ethylene glycol) Dimethacrylate, 2,2-Dimethoxy-2-Phenylacetophenone

Centrifuge Polypropylene Tubes (50ml), Tube Racks, Balance, Pipette, Pipet Tips, Transfer Pipets with Standard Bulb, Vortex Genie 2 Mixer, Weigh Boats, Spatula, Glass Tubes (Inner diameter 12mm), Rubber Stopper (diameter 12mm), Vacuum Oil, UV Oven, Incubator, Refrigerator, Laser Cutter

**3.Steps:**

(As an example, the following steps are for the synthesizing of 10 wt% specimens. For 20, 40 wt% specimens the procedure is the same but with different chemical ratios, refer to **Table 1**. The absolute amount of each chemical is subjected to change based on the number of specimens need to be synthesized.)

**Step1**: Put the polypropylene tube on the balance, and then zero the balance. 

**Step2**: Transfer 1.24ml DEGDMA into the polypropylene tube using a pipette with

pipet tip. Measure the mass using the balance.

**Step3**: Change a new pipet tip. Transfer 2.84ml PEGDMA into the polypropylene tube using a pipette with pipet tip. Measure the mass using the balance. Make sure the mass ratio of DEGDMA: PEGDMA is 3:7.

**Step4**: Change a new pipet tip. Transfer 45.92ml tBA into the polypropylene tube using a pipette with pipet tip. Measure the mass using the balance. Make sure the mass ratio of DEGDMA: PEGDMA: tBA is 3:7:90.

**Step5**: Put a weigh boat on the balance. Zero the balance. Add the photoinitiator (2,2- Dimethoxy-2-Phenylacetophenone) to the weigh boat using a spatula until the mass of the photoinitiator is 0.1% of the mass of the polymer solution.

**Step6**: Add the photoinitiator to the polymer solution. Screw the cap on tightly. Put the tube on the mixer for 1-2 mins. Make sure the photoinitiator is fully dissolved.

**Step7**: Seal one end of the glass tube using a rubber stopper. Secure the sealing with vacuum oil. Make sure there is no leaking.

**Step8**: Inject the polymer solution into the glass tube using a transfer pipet with bulb. Seal the other end of the glass tube using a rubber stopper. Secure the sealing with vacuum oil. Make sure there is no leaking.

**Step9**: Put the sealed glass tube into the UV oven.

**Step10**: Turn on the UV oven. Expose the glass tube containing polymer solutions to UV light for 20 mins in total. For the first 10 mins, rotate the glass tube every 1 minute to get a uniform exposure to the UV light. For the next 10 mins, do this every 2 or 3 mins.

**Step11**: Turn off the UV oven. Transfer the glass tube into the incubator. Equilibrate at 70°C for 60-90 mins.

**Step12**: Cool down the specimen in a refrigerator. Separate the cylindrical polymer specimen from the glass tube. Cut the specimen into several short ones with desired length using a laser cutter.

^ Mass Ratio (DEGDMA:PEGDMA: tBA)      ^ Volume Ratio (DEGDMA:PEGDMA: tBA)       ^ 50ml in total (DEGDMA+PEGDMA+ tBA)          ^
| 3:7:90 (10 wt%)    | 2.7726:6.3694:102.8571     | 1.24ml+2.84ml+45.92ml        |
| 6:14:80 (20 wt%)    | 5.5453:12.7389:91.4286    | 2.53ml+5.81ml+41.67ml                  |
| 12:28:60 (40 wt%)    | 11.0906:25.4778:68.5714     | 5.27ml+12.12ml+32.61ml        |

Table1. Mass ratios and volume ratios of three chemicals for 10, 20 and 40 wt%