Dear Anbu, the answer to your question depends on the route of synthesis you intend to use. Controlled radical polymerizations (according to IUPAC more correctly reversible deactivation radical polymerization (RDRP) Jenkins, A. D.; Jones, R. G.; Moad, G. Pure Appl. Chem. 2010, 82, 483-491.) are often used. They are easier but inferior in many ways compared to living polymerization methods. Notably, a big problem of RDRP is the loss of control at high monomer consumption. Thus, triblock copolymer synthesis will have limits. Moreover, RDRP produces C-C backbones, which are non-biodegradble. This should be a concern in preparation of biomaterials such as gene delivery vectors. Polypeptide synthesis is rather difficult for preparation of clean triblock copolymers, but the polymers are biodegradable.

Also possible strategies on characterization of your product is dependent on your synthetic approach. In general, 1H-NMR is typically useful to obtain the relative amount of your different blocks, if you have a reliable, characteristic end-group, NMR may also give you the molar mass, or degree of polymerization of the different blocks. However, you need to be very careful to use an appropriate solvent which is non-selective for all three blocks. This may be challenging, depending the chemical nature of your blocks. Gel permeation chromatography must be used with great care, since typically dn/dc of the different blocks is different and correct analysis may be quite challenging

Best regards

Robert

Dear Mozhi,

You need to use one of the controlled polymerization techniques such as ATRP or RAFT in order to control the chain growth of the each block. So you can control the degree of polymerization.

Dear Mozhi, I agree with Engin Acikalin in the comment above. ATRP or RAFT give you a high degree of control over the polymerization. I know its advertising my work, but we always use ATRP with a simple adjustment to enhance the deactivation and give you even more control.

Check out the original paper:3D Single Cyclized Polymer Chain Structure From Controlled Polymerization of Multi-Vinyl Monomers: Beyond Flory-Stockmayer Theory, Journal of the American Chemical Society 2011,

or the one where we used this chemistry for gene delivery:

Single Cyclized Molecule Versus Single Branched Molecule: A Simple And Efficient 3D “Knot” Polymer Structure For Nonviral Gene Delivery, Journal of the American Chemical Society, 2012

Please get in touch if you would like a simple step by step protocol for this chemistry. I have one written up.

All the best,

Ben (www.newlandresearch.net)

The best and possibly the only true control is offered by living anionic polymerization, however the feasibility of this will depend on the monomers you want to use.

I suggest ATRP and RAFT for good control of polymerization. To purify the product, you can use dialysis method. For characterization of molecular weight, degree of branching you may want to consider asymmetric field flow fractionation coupled with light scattering, uv and viscometer detectors. This will eliminate interaction problem between your synthesized materials with typical GPC/HPLC column. For size of your triblock, you can use dynamic light scattering.

Anbu, I agree with Engin, Ben, CHristopher, and Yusof. While ATRP and RAFT have been suggested, I would start with ATRP and try to scale up using RAFT if needed. YOu did not indicate if you were mianlyinterested in symmetrial ABA triblocks or asymmetrical ABC triblocks, but both can be pursued with ATRP. You maybe interested in the ABA we described two years ago [“Triblock copolymer based on poly(propylene oxide) and poly(1‐[11‐acryloylundecyl]-3‐methyl-imidazolium bromide);” J. Texter, V. Arjunan Vasantha, R. Maniglia, L. Slater, and T. Mourey. Macromol. Rap. Com. 33, 69-74 (2012)], where the endblocks are cationic. As Yusof suggested, we used dialysis to purify the product and lyophilization (freeze drying) to recover from water. We used hexafluoroisopropanol as a carrier solvent in GPC, because otherwise teh extrmemely amphiphilic triblocks would stick to the column; this is a general problem for cationic polymers and GPC.

I think RAFT polymerization is an easy straightforward method to prepare triblock copolymer irrespective of vinyl type monomer type. You can look into literature for the related polymers to get information what type of CTA and conditions are used.

Thanks to all for your suggestion.

As mentioned by Dr. Engin Acikalin, ATRP and RAFT polymerization should be a feasible method.

Most of the people has already suggested about the method to be followed for the preparation of triblock copolymer. I am agree with them and according to me, ATRP will be better. But, I want to mention here one thing, whatever be the method, you follow, it will be better to do GC analysis, taking out little aliquot from the reaction mixture after a certain time interval as it will help you to measure the rate of reaction and to determine the total time span required to continue the reaction.