It is often useful to draw a graph (in the formal sense, nodes connected by edges) of the possible causal relationships that are relevant for your research project. The following book is an introduction to these (http://bayes.cs.ucla.edu/PRIMER/). One important aspect of Pearl's work is that it applies to both quantitative and qualitative relationships.

The methods section in this article may be of use to you:

“Components of effective social work practice in mental health for young people

who are users of multiple services”. Munford, R. & Sanders, J. Social Work in Mental Health, 13 (5): 415-438.

Dear Sanam,

I guess you refer to the Sequential Exploratory form of Mixed Methods design (there is also a Sequential Explanatory form, where the quantitative research precedes the qualitative one). I do not think you need different conceptual frameworks for the qualitative and quantitative study. A conceptual framework is based on theoretical underpinnings which are necessary to attain your allover research objectives. It is at an abstract level. The ideas about the qualitative and quantitative research stem from the theoretical points of view. These ideas are more like the breakdown' (operationalization) of your conceptual framework which come later. I would not suggest to include it in your introduction section, but in a separate section on methodology. 

All the best.

I agree - outline all your methods in  your methodology chapter so that the reader is clear about your methods and justification for these.

 You would need only one conceptual framework. A conceptual framework acts as a guide to clarify either outcome of your research or justifies your position (methods, literature review etc) in the research. Two different conceptual frameworks (for qualitative and quantitative) would bifurcate the central themes into two different direction, a should avoid this.

Dear Sanam

I agree with Kirtie and Robyn. Your mixed-methods design is sequential exploratory. The qualitative study is the protagonist and guides the quantitative phase. The theoretical framework should develop mainly in the qualitative phase. You can lead by schemes like "Grounded Theory". In other words, you can develop the theoretical framework simultaneously with the qualitative study. From the theoretical framework and the qualitative findings you can derive hypotheses. Finally in the quantitative phase (where you no longer need a new theoretical framework) you could test the hypotheses.

Regards

Great answers and always be clear about your research questions as these guide your procedures.

I don't see why you need a separate conceptual framework (let alone two of them), since you already have a coherent research design. The key underlying issues are whether you have a well justified set of research questions and whether your methods are appropriate for answering those question.

I agree - one of the challenges my students face is keeping focused on the research questions so having supervision is a good strategy.

Thanks alot for valuable answers and suggestions. My queries have been answered to a great extent. 

I'm a little late the party, but I would add a couple of things.  I would draw from the existing research literature to inform the qualitative portion of your study.  The literature should suggest your research questions for that piece, as others have suggested.  Once I have the qualitative information that shores up the "holes" in the literature, then I would posit my conceptual framework to guide the quantitative portion.  At the end of that study, you would revise your framework.  That would then allow you to move to a new project of designing an instrument, if applicable, to test or validate the framework.

 research methodology can be drawn from the existing review of the literature and the research  gap (that can be found by the review of the literature) , so the methodology is determined by the field of study, the problem of study based on the previous studies. Conceptual framework is made by the logic of research design and what is really you want to study

It's difficult to respond to your question in more than general terms because your research topic and context is unknown to us. However, I start by saying that it's important to remember that methods (i.e. quantitative and//or qualitative techniques used to collect data) are not the same as methodology (i.e. research paradigm - positivist/naturalistic). The reasons researchers mix data collection methods in a study vary, but they're hopefully based on the rationale that mixing methods in the selected way will provide the best way to resolve the research problem/question....and it's my view that this is what should be at the heart of your defence of the methods you're employing in your study.You've spoken of using "a sequential mixed methods design where qualitative leads into quantitative", but this sounds like a grounded theory approach, particularly if your design involves a single qualitative phase followed by a single quantitative phase in which the results of the analysis of your phase 1 (qualitative) data feed into the design of a research instrument for phase 2). But then you speak of "different objectives for each part", which makes me question if you'll ultimately be triangulating data whereby you have various quantitative data and qualitative data that constitute multiple sources of evidence that you will analyse inductively to draw your conclusions. This, then, is a mixed methods approach.